What is the way to get rid of doubts and obsessions that prevent stability in faith and the application of acts of worship, despite uttering the Shahada and knowing the truth?

The confusion of truth with falsehood stems from a lack of religious knowledge, succumbing to obsessive whispers and doubts, neglecting self-purification, and listening to the sophistries of doubters. Action — including calling people to Allah — requires insight and knowledge. For this reason, the scholars of the Salaf warned against reading the books of philosophers. One must cut off the fleeting thoughts of the self and the whispers (of Shaytan), and seek refuge in Allah from Satan. It is advised to bring to mind the clear and decisive evidence and to weigh doubts against it. One must not neglect self-purification and caring for the heart, for the Prophet, peace and blessings be upon him, said: "Indeed, there is a piece of flesh in the body, if it is sound, the whole body is sound, and if it is corrupt, the whole body is corrupt. Indeed, it is the heart."