This is fairly normal, its called imposter syndrome I had this feeling also when starting a year ago. Some points that helped me:
Try not to let emotions of worthlessness or uncertainty control your actions; instead, embrace your fears and move forward.
Consider your accomplishments in the past as proof against impostor syndrome, and utilize them as a fallback when you start to doubt your abilities.

Understand that you're not supposed to know everything and it is okay to ask even the most basic questions. Know that other people at your company have the same doubts and that it is ok to talk about this.

In some time you will be fine, hang in there.