At this point there’s still a lot to learn to use Git in a team, where it really shines. There are many resources for learning about Git in depth; I would recommend the free and popular Pro Git book. If you’re only getting started with version control there are a few things to keep in mind:
Almost any destructive operation can be reversed, if you’re careful. Slow down, maybe experiment in a copy of the repository, and you won’t lose changes by accident.
Track the source files and the instructions (or code) to transform it into other formats, but not the files generated from the sources. Tracking generated files usually leads to a messy and bloated repository history. That’s not to say you shouldn’t keep the generated files somewhere!
In the same vein it’s better to track the plaintext version of something than any binary representations. Some formats can be losslessly converted from a binary to a text format, for example by decompressing an SVGZ file, saving as FODT rather than ODT, or exporting a spreadsheet to CSV.