How can one get rid of doubt in belief in God, which began six years ago, despite reading books on atheism and Islam, and the desire to return to absolute faith and tranquility?

A Muslim should not read books on atheism without knowledge and certainty. Rather, he should remove any doubts that cling to his heart by contemplating the Holy Quran, frequently remembering Allah, supplicating, and reading specialized books such as: "Physics and the Existence of the Creator" by Ja'far Sheikh Idris, "Allah Manifests in the Age of Science" by Al-Damardash Abdul-Majeed Sarhan, "Islam Challenges" by Wahiduddin Khan, and "A Struggle with Atheists to the Bone" by Abdur-Rahman Al-Maidani. These books contain scientific and factual evidence, and testimonies from geniuses that affirm the existence of Allah.