764 Errors After adding admob

First I was on unity 2019.2.x version then I updated to 2019.3.x version.
On 2019.2.x I had google play services with online save.
Then I added admob for ads (after updating to 2019.3.x) and when I tried to build for android there was 764 errors:
1x OperationCanceledException: The operation was canceled.
2x CommandInvokationFailure: Gradle build failed.
1x java.lang.RuntimeException: Duplicate class android.support.v4.app.INotificationSideChannel found in modules classes.jar (:androidx.core.core-1.0.0:) and classes.jar (:core-1.1.0:)
And a lot of (700+)x Duplicate class android.support.v4.os.IResultReceiver$Stub$Proxy found in modules classes.jar (:androidx.core.core-1.0.0:) and classes.jar (:core-1.1.0:)
and 1x CommandInvokationFailure: Gradle build failed.

Any ideas what happened and how to fix that? It works in editor...