If you want to contribute to the engine / editor here is some info.
This is a list of issues that have been marked as good first issues for people who want to begin contributing.
If you want to contribute to the editor make sure you’re on the editor-dev branch
Some of your questions are answered here, but you should read most of the readmes next to it too.
You’ll need to get the editor / engine building on your local computer and that will be the first hurdle you’ll have to overcome to meaningfully begin contributing. Some of the “good first issue” issues are probably relatively easy to do, but it depends on you too and how much you already know / are willing to invest into learning more of.