Is evolution rejected in its entirety, and what is the way to strengthen faith and certainty in facing doubts and whispers resulting from studying evolution and philosophy and intermingling with non-Muslims?

The greatest means of steadfastness is supplicating to Allah Almighty, for the hearts of the servants are between two of His fingers, may He be glorified, turning them as He wills. The Prophet, peace and blessings be upon him, used to often say: "O Turner of hearts, make my heart firm upon Your religion."

If the studies involve doubts that cannot be repelled, and it is feared that they may be a cause of tribulation (fitna), then it is obligatory to abandon them. If it is possible to study in a Muslim country, that is more preferable due to the abundance of causes of tribulation in non-Muslim lands. Emigration from such lands may become obligatory if a Muslim fears tribulation for himself.

Mere whisperings (waswasa) regarding faith do not affect it, as long as the person experiencing them repels them.