Can't create an APK after exporting to AndroidStudio Project

Hi everyone, Recently, Google started to demand asking for permissions on runtime (android 6.0). So in order to do so, I have to export an Android Studio project out of my Unity3D project, and remove the automatically added permissions, such as READ_PHONE_STATE, and require them later in the game.

The problem is, that I can't create an APK file, out of the project. Can't even run it because AS fails to build the project. The first problem I dealt with, was: at last, I just removed all "compile project("xyz")" lines that contained Google play services, on build.gradle. and then I got an error I could not solve:

 :myApp:transformClassesWithDexForRelease
 To run dex in process, the Gradle daemon needs a larger heap.
 It currently has approximately 910 MB.
 For faster builds, increase the maximum heap size for the Gradle daemon to more than 2048 MB.
 To do this set org.gradle.jvmargs=-Xmx2048M in the project gradle.properties.
 For more information see https://docs.gradle.org/current/userguide/build_environment.html
 
 AGPBI: {"kind":"error","text":"PARSE ERROR:","sources":[{}]}
 AGPBI: {"kind":"error","text":"unsupported class file version 52.0","sources":[{}]}
 AGPBI: {"kind":"error","text":"...while parsing com/heyzap/UnusedStub.class","sources":[{}]}
 AGPBI: {"kind":"error","text":"1 error; aborting","sources":[{}]}
 
 :myApp:transformClassesWithDexForRelease FAILED
 
 FAILURE: Build failed with an exception.
 
 * What went wrong:
 Execution failed for task ':myApp:transformClassesWithDexForRelease'.
 > com.android.build.api.transform.TransformException: java.lang.RuntimeException: com.android.ide.common.process.ProcessException: java.util.concurrent.ExecutionException: com.android.ide.common.process.ProcessException: org.gradle.process.internal.ExecException: Process 'command '/Library/Java/JavaVirtualMachines/jdk1.8.0_91.jdk/Contents/Home/bin/java'' finished with non-zero exit value 1

any help from here? thanks!