Punctuation can be tricky (for some) to master, even for natives in their own languages! This is a useful online site, full of information which lists, explains, and demonstrates English punctuation characters in an easy-to-follow manner.
If anyone wants to chat about comma usage, i would be happy to help! It is something i go over a lot with my B1 class and of course there is always the controversial (but correct!) Oxford comma to discuss too.