Answer 1

Always refer to official docs first, they are usually a one stop place e.g. it has everything you need ;)

https://expressjs.com/en/5x/api.html

Make use by following the examples and understand what's going on then try to remake the examples without any help. Move on once you can completely remake the example with 0 help!
After you feel confident, make projects then look at advanced projects to compare yours to