Vespucci is great once you get the hang of it! No need to be to afraid, as you will get to review your changes before you upload (unlike in StreetComplete). Just abort if there's something weird looking.
Find something you want to fix, and then head to the wiki to see how it's supposed to be mapped. E.g. maybe you want to add a bench. The wiki tells you that it should be either a single node or a way, and that it should be tagged amenity=bench
. (It also lists a bunch of other tags that may be used). Then just try to implement that with Vespucci. Most of it is just tagging. (There is actually a bench preset in Vespucci, so you could just search for it there, but this is the general process.) Refer to the wiki, a lot. We are basically lawyers interpreting the wiki.
As a beginner you can also check the "I would like someone to review my changes" box when uploading, if you're unsure of something.