It is certain that you will have compile errors since this app uses a file google-services.json in order to connect to firebase, and I can't and I don't provide that in the repo (added to gitignore) because it contains private information to my firebase project. Thus, you must do it yourself. Create a firebase project with the same name as my app: Chess4Android. See here on how to do it
Even if you just wanted to install the app through the .apk that can be generated, the use of the firestore database has usage quotas and some terms of service regarding what you can put in it or use it for, so I can't just make it's access public to strangers.
But you can have the .apk with the version that doesn't use firebase :)
Transfer it to your phone and install.