Dealing with New Hire Imposter Syndrome

I started a new role that I feel under qualified for. In my previous role, I was on the team for many years and naturally became one of the most senior people on the team. I was a full stack engineer and new a lot about React and APIs, however, my new role is completely different (mainly about infrastructure and terraform). In my previous role, I felt so comfortable and knew so much about where the code lies, how everything fit together, and all the people connections I had there. How do I stop missing my previous role and move on? Also, how do I get up to speed with all the new technology I have to learn quickly? I already feel so behind and I keep asking for help because I don't know where anything is. I don't feel like a senior engineer in my new role and I'm worried what other people on the team are thinking about my lack of infrastructure experience.