best thing is remembrance of Allah as He said

Holy Quran 13:28
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الَّذِينَ آمَنُوا وَتَطْمَئِنُّ قُلُوبُهُم بِذِكْرِ اللَّهِ ۗ أَلَا بِذِكْرِ اللَّهِ تَطْمَئِنُّ الْقُلُوبُ

Those who have believed and whose hearts are assured by the remembrance of Allah. Unquestionably, by the remembrance of Allah hearts are assured.”

Can you start doing Aamal e Ashura for 40 days and read surah fath after Fajr and sura Insan after isha kindly spend some time in reading of translation of Quran and tafseer inshallah understanding of Quran will remove the evil thoughts