How to overcome imposter syndrome

I recently started a new job and I absolutely love it. The issue is, it’s a very complex business and there’s a lot to do, so I feel like it’s taking me a lot longer to get up to speed than in previous jobs. My colleagues also seem to be super competent.

Lately I was asked to take the lead on a few calls or matters and I just feel like I’m not where I should be in terms of delivery and output. I’m not sure what the expectations are but I feel awkward sometimes as people ask me questions and look at me expecting a straightforward answer, which I don’t have.

I guess as I’m still on probation I’m not 100% confident and keep questioning whether they are happy with me or not. Any advice?