Hello Alefe,
That version of Gradle that you’re using will cause issues with Android builds. I recommend sticking to the recommended 6.7.1.
Please have a look at this forum post for more information: How to Resolve Gradle Build Error: "The option setting 'android.enableR8=false' is deprecated..."
If the information on the forum post does not resolve your issue, please reply back here, not on the guide itself 