Android app and Push notifications not working

Dear friends,

I’m trying to make an android executable to use push notifications service but having some troubles.
I’m using android studio to adapt my app to create communications with Firebase and with my server. (
I already have a firebase project.
But, I download the android source code to my android studio but I cannot run the program or generate an executable.
I used the android code from github (mattermost-mobile) and gradle is missing. I cannot make a communication with firebase.
I used also this android classic, I can make a sync, but when I try to run the program or create an executable to use in android fone it starts with errors. I solved some but still continue with problems…
I made some code changes, like the page says (
I install SDKs and SDK tools.

Thank you for your help.
Best regards