My response would be that (1) religion is more something you do, not so much think, and (2) religion is meant to be a struggle. Furthermore, "inner peace" requires moving into a thought space that's orthogonal to doubt https://blogs.ancientfaith.com/asd/2016/08/21/christians-allowed-doubt/ - I would also answer that what prayer means is develop a relationship, which is orthogonal to doubt as well. One way to think about doubt is also to imagine yourself in solitary confinement like maybe you're a Christian imprisoned by Romanian communists or a non-violent, unarmed, peaceful J6 protestor unjustly put in six months of solitary confinement just like in an authoritarian regime - How do you avoid going crazy? Prayer is one answer.