Need to quickly learn Sketch - to create web app mock-ups
What's the quickest way to learn Sketch for someone with no design background? I want to create mock-ups for a side project.
How do I learn the rudimentary basics of design? (the kind explained in the material design docs). For example, number of pixels that a web page margin should be, how to make good bread crumbs, etc.
I tried Fiverr but I'm unable to get good looking designs. Tried with multiple designers charging 50 USD per page.