Compile APK! From sources. APKTOOL (apktool.yml-not found) Android Sudio (no generate apk button)?

Question

Android

Help compiling APK from GitHub sources. ( https://github.com/nextcloud/android)
Via APKTOOl error with brut.directory.PathNotExist: apktool.yml and with Android Studio there is no Generate Signed APK button.
Help!)

Answer 1

Why is there no button? It's easy to find
About creating a signature is well written in the dock