How can one overcome fear and anxiety regarding jinn and demonic possession (mass) when sleeping, especially when in an environment where there is much talk about these matters, and what is the advice and solution for this problem?

We advise you to be courageous, to trust in Allah Almighty, to rely on Him, and to rid yourself of the illusions of fear. Supplicate to Allah and seek refuge in Him from cowardice, for the Prophet, peace and blessings be upon him, used to say: "O Allah, I seek refuge in You from anxiety and sorrow, from weakness and laziness, from cowardice and miserliness, and from the burden of debt and being overcome by men." You should also maintain the prescribed remembrances (adhkar) at their proper times, and frequently recite the Quran, especially Surah Al-Baqarah, Ayat Al-Kursi, Surah Al-Ikhlas, and Al-Mu'awwidhatayn (Surah Al-Falaq and Surah An-Nas) after every prayer and before sleeping, and recite the last two verses of Surah Al-Baqarah every night.