Cant build android APK after Firebase integration

Hi! I am working an a mobile app (for Android only), but I got stuck with integrating Firebase. When I am not using any of the Firebase packages, I can simply build the app. However, as soon as I add the Core, Storage and Firestore packages, my app can no longer be built.

Error message:

Note: ...\Temp\gradleOut\unityLibrary\src\main\java\com\unity3d\player\UnityPlayerActivity.java uses or overrides a deprecated API.

And also:

CommandInvokationFailure: Gradle build failed. ...\Unity\Hub\Editor\2020.2.3f1\Editor\Data\PlaybackEngines\AndroidPlayer\OpenJDK\bin\java.exe -classpath "...\Unity\Hub\Editor\2020.2.3f1\Editor\Data\PlaybackEngines\AndroidPlayer\Tools\gradle\lib\gradle-launcher-5.6.4.jar"

Specs:

• Unity 2020.2.3f

• Firebase Core, Storage, Firestore 6.15.2

Does anyone have a clue what is happening?