You can help us close Issues which are marked with the "Contributions welcome" tag. For example, at [this link](https://git.selfprivacy.org/kherel/selfprivacy.org.app/issues?q=&type=all&state=open&labels=118) you will see tasks tagged "Contributions welcome" for the main application.
We cannot approve major changes without the approval of the core developers. Of course you can create a fork of the project, but if you want to get approval, please discuss the proposed changes in one of the project chats:
The server side of SelfPrivacy uses the NixOS distribution, and a daemon program written in Python called SelfPrivacy API. The daemon works to provide a link between your server and SelfPrivacy app. You can read [here](https://git.selfprivacy.org/SelfPrivacy/selfprivacy-rest-api/src/branch/master/CONTRIBUTING.md) about how to test and make changes to the SelfPrivacy API.