CS Career Questions

I’m doing interviews for companies that would involve API integrations. I’ve done a couple now where I was given some general API information (some intentionally unclear, some more clear) and I felt I didn’t do well. Mainly I was nervous, and felt very pressured just to understand how the different parts of the APIs interact with each other and should be interacted with. This is despite doing this for work and myself not feeling as nervous doing more common coding tests which I don’t do as much at work(thanks to doing examples on hackerrank, Leetcode helping me feel more comfortable).

So what are the resources I should leverage to practice API integrations? How should I go about practicing? Especially considering that I do need to perform in a certain way during interviews.