You haven’t said if you want to work on the code or only want to run the software, but if it’s the latter you don’t actually need the code usually. There’s usually a Releases page (I believe it can be found on the right side bar) that will have the software built and packaged for different systems. So unless it’s not available for your OS and you need to build it yourself (which can be a bit of a pain to figure out) you don’t need the code.

My understanding is, you’re routing your traffic through 3 nodes, so the slowest of those 3 will bottleneck the entire process. Unfortunately it’s just how Tor works.