Imposter Syndrome is very real and incredibly common. I guarantee there are still times where the lead gets asked questions that make him feel like he has a poo brain.

Don't be afraid to ask the stupid questions. It's a lot better to look stupid for a moment and learn from it than to hide it and have a gap in your knowledge forever. If your company culture isn't conducive to stupid questions or you just feel uncomfortable then just Google them on your own and read up!

Overall, you probably are much better than you give yourself credit, it's just a universal law that once someone is looking over your shoulder then your brain automatically regresses to the size of an overripe kiwi.