JINN POSSESSION OR DEMONIC POSSESSION
Jinn Possession (or Masaha)is a kind of sickness. If a person who has this sickness is rational, then he has the choice and he will be brought to account for his words and actions. But if this sickness has overwhelmed him to the point that he has lost his mind and free will, then he is like one who is insane and is not accountable. Hence in Arabic the word MASS (possession) is used to refer to junoon (insanity).
The fact that we cannot see the jinn does not mean they do not exist either. This is the view of the materialists of our age and those who followed in their footsteps. Indeed, how many are there things that our eyes cannot see but whose effects are noticeable? While the examples are many and varied. Include, air, electricity and limited to this.
It is possible for jinn to possess humans. Allah says in His Book: “Those who eat riba [usury] will not stand (on the Day of Resurrection) except like the standing of a person beaten by shaytan leading him to insanity.” Quran Surah Baqrah 2:275
Shaykh al-Islam IbnTaymiyah (may Allah have mercy on him) said:
The fact that a jinni may enter the body of a human is proven by the consensus of the imams of Ahl al-Sunnah wa’l-Jama’ah (the larger body of Muslims who are upon the prophetic traditions). Allah says (interpretation of the meaning): “Those who eat riba [usury] will not stand (on the Day of Resurrection) except like the standing of a person beaten by shaytan leading him to insanity.”Quran Surah Baqrah 2:275 
Al-Qurtubi said in his Tafseer (exegesis): “This ayah (verse) is proof that those people are wrong who deny that epilepsy is caused by the jinn and claim that its causes are only physical, and that the Shaytan does not enter people or cause madness.”
Ibn Katheer said in his Tafseer, after mentioning the ayah quoted above: “They will not rise from their graves on the Day of Resurrection except like the way in which the epileptic rises during his seizure, when he is beaten by the Shaytan. This is because they will rise in a very bad state. Ibn ‘Abbas (may Allah be pleased with him) said: the one who consumes riba will rise on the Day of Resurrection crazy and choking.”
Their powers are greater than those of man, as Allah says: “An ‘Ifreet (strong one) from the jinn said: “I will bring it [the throne of the Queen of Saba] to you before you rise from your place.”Quran Surah Naml 27:39
There was a great distance between Sulayman (peace be upon him) and the Queen of Saba (Sheba).
Allah has enabled the jinn to change shape and to fly, etc, but despite their great powers they have no control over the righteous slaves of Allah. Allah says : “Verily, My slaves (i.e. the true believers of Islamic Monotheism) — you have no authority over them. And All-Sufficient is your Lord as a Guardian.”Quran Surah Isra17:65
“And he (Satan) had no authority over them, except that We might test him who believes in the Hereafter, from him who is in doubt about it.”Quran SurahSaba 34:21
The Prophet (ﷺ) that “The Shaytan flows through the son of Adam like blood.” Sahih al-Bukhari 3281 and 7171
‘O Messenger of Allah, I get confused during my prayer, until I do not know what I am doing.’ He said: ‘That is Satan. Come here.’ So I came close to him, and sat upon the front part of my feet then he struck my chest with his hand and put some spittle in my mouth and said: ‘Get out, O enemy of Allah!’ He did that three times, then he said: ‘Get on with your work.’” ‘Uthman said: “Indeed, I never felt confused (during my prayer) after that.” SunanIbnMajah 3548 
There is nothing wrong with the Muslim reciting ruqyah for himself. That is permissible; indeed it is a good Sunnah, for the Messenger (peace and blessings of Allaah be upon him) recited ruqyah for himself, and some of his companions recited ruqyah for themselves.
It was narrated that ‘Aa’ishah (may Allaah be pleased with her) said: When the Messenger of Allaah (ﷺ) was ill, he would recite al-Mi’wazatayn over himself and spit drily. When his pain grew intense, I recited over him and wiped him with his own hand, seeking its barakah (blessing).” Sahihal-Bukhari, 4728; Sahih Muslim, 2192 For More: Dua and Azkar 
With regard to the du’aa’ that is prescribed for the Muslim to say if he wants to recite ruqyah for himself or for someone else, there are many such du’aa’s, the greatest of which are al-Faatihah and al-Mi’wadhatayn.
A group of the Companions of the Prophet (peace and blessings of Allaah be upon him) set out on a journey and travelled until they made came near one of the Arab tribes. They asked them for hospitality but they refused to do so. Then the leader of that tribe was stung, and they tried everything but nothing helped him. Then some of them said, Why don’t you go to those people who are staying (nearby)? Maybe some of them have something. So they went to them and said, O people, our leader has been stung and we have tried everything and nothing helped him. Do any of you have something? One of them said, Yes, by Allaah. I will perform ruqyah for him, but by Allaah we asked you for hospitality and you did not give us anything, so we will not perform ruqyah for you unless you give us something in return. So they agreed on a flock of sheep, then he started to blow on him and recite Al-hamduLillaahiRabbil-‘Aalameen. Then he recovered quickly from his complaint and started walking, and there was nothing wrong with him. Then they have them what they had agreed to, and some of them (the Sahaabah) said, Let us share it out. The one who had performed ruqyah said, Do not do anything until we come to the Prophet (ﷺ) and tell him what happened, and we will wait and see what he tells us to do. So they came to the Messenger of Allaah (peace and blessings of Allaah be upon him) and told him what had happened. He said, “How did you know that it is a ruqyah?” Then he said, “You did the right thing. Share them out, and give me a share.” And the Messenger of Allaah (ﷺ) smiled.Sahih al-Bukhari, 2276, and Sahih Muslim, 2201
It was narrated that ‘Aa’ishah (may Allaah be pleased with her) said: When the Messenger of Allaah (ﷺ) was ill, he would recite al-Mi’wazatayn over himself and spit drily. When his pain grew intense, I recited over him and wiped him with his own hand, seeking its barakah (blessing).” Sahihal-Bukhari, 4728; SahihMuslim, 2192
Ibn ‘Abbaas (may Allaah be pleased with him) said: The Prophet (ﷺ) used to seek refuge for al-Hasan and al-Husayn, and he would say: “Your father [ meaningIbraaheemm peace be upon him] used to seek refuge with Allaah for Ismaa’eel and Ishaaq with these words: 'U'eezubikalimaatil-laahit-taammati min kulli shaytaanin wahaammatin, wa min kulli 'aynin-laammatin. (read this 1 time)(Meaning: I seek refuge in the perfect words of Allaah, from every devil and every poisonous reptile, and from every evil eye).’” Sahih al-Bukhari, 3191
o The Muslim must, above all else, arm himself with the weapon of faith and righteous deeds, for these are the best provision he may have and the best means of foiling the plots of the devils among mankind and the jinn.
o You have to strengthen your relationship with Allah, for He is the One on Whom you should depend. Remember Allah a great deal in all situations, and strive to keep your tongue busy constantly with dhikr (remembrance of Allah). No one can find any better protection against the shaytan than the remembrance of Allah.
It was narrated in a saheeh (authentic) report from the Prophet (ﷺ) that Allah enjoined five things upon YahyaibnZakariyya, which he was to do and to command the Children of Israel to do, one of which was: “I command you to remember Allah, for the likeness of that is that of a man whose enemy comes after him, until he comes to a strong fortress where he protects himself from him. Similarly, a person cannot protect himself against the shaytan except by remembering Allah.”Sahih at-Tirmidhi 2863
o Constantly recite the dhikrs(Zikr or remembrance) narrated from the Prophet (ﷺ), such as the dhikr when entering the toilet, when having intercourse, when hearing the braying of a donkey, when entering the house, in the morning and the evening, when going to sleep, and in other circumstances and at other times for which a specific dhikr has been narrated from the Prophet (ﷺ). 
These dhikrs have been compiled in books such as al-Adhkar by al-Nawawi, al-Kalim al-Tayyib by IbnTaymiyah, and Hisn al-Muslim by al-Qahtani [the latter is available with English transliteration and translation under the title “Fortress of the Muslim – Invocations from the Quran and Sunnah”, Published by Darussalam, Riyadh – Translator].
o You should also read a lot of Quran in the house, especially Surah al-Baqarah. Ahmad and Muslim narrated from Abu Hurayrah (may Allah be pleased with him) that the Messenger of Allah (ﷺ) said: “Do not make your houses (like) graveyards, for the shaytan flees from a house in which Surah al-Baqarah is read.”
o You should also purify your house of everything in which there is disobedience towards Allah, such as keeping images and dogs. Abu Talhah (may Allah be pleased with him) narrated that the Prophet (ﷺ) said: “The angels do not enter a house in which there is a dog or an image.” Sahihal-Bukhari 4002 and 5949, Sahih Muslim 2106 
* Surah Al-Faatihah
* Surah Al-Baqarah Ayaat 285, 286
* Surah Al-A'raaf, Ayaat 54-56
* Surah Ikhlaas (surah 112)
* Surah falaq (surah 113)
* Surah Naas (surah 114)
Bismillaahil-lazee laa yadurru ma'asmihi shay'un fil-'ardi walaa fis-samaa'i wa Huwas-Samee 'ul- 'Aleem (read this 3 times, Morning and Evening)
Meaning: "In the name of Allah, when Whose name is mentioned nothing on Earth or in Heaven can cause harm, and He is the Hearer, the Knower" SunanAbiDawud 5088 and Jami Timidhi, Hadees: 3388
اللّٰهُمَّ رَبَّ النَّاسِ أَذْهِبِ الْبَاسَ،اشْفِهِ وَأَنْتَ الشَّافِي، لَا شِفَاءَ إِلَّا شِفَاؤُكَ، شِفَاءً لَايُغَادِرُ سَقَمًا
Allahumma Rabban-naas Azhibil baas Shaafi waanta sh-shaafi, la shifa’a illa shifaa’uka, shifa’an la yughadiru saqama.
Meaning: "O Allah, the Lord of the people! Remove the trouble and heal the patient, for You are the Healer. No healing is of any avail but Yours; healing that will leave behind no ailment." Sahih al-Bukhari 5743 
Allah knows best
  https://islamqa.info/en/42073