Want to add unity or admob advertising, but there is always the same error in my logcat.. pls help

) AndroidJavaException: java.lang.ClassNotFoundException: com.unity3d.ads.IUnityAdsListener
java.lang.ClassNotFoundException: com.unity3d.ads.IUnityAdsListener
at java.lang.Class.classForName(Native Method)
at java.lang.Class.forName(Class.java:453)
at java.lang.Class.forName(Class.java:378)
at com.unity3d.player.UnityPlayer.nativeRender(Native Method)
at com.unity3d.player.UnityPlayer.c(Unknown Source:0)
at com.unity3d.player.UnityPlayer$e$2.queueIdle(Unknown Source:72)
at android.os.MessageQueue.next(MessageQueue.java:394)
at android.os.Looper.loop(Looper.java:142)
at com.unity3d.player.UnityPlayer$e.run(Unknown Source:32)
Caused by: java.lang.ClassNotFoundException: Didn’t find class “com.unity3d.ads.IUnityAdsListener” on path: DexPathList[[zip file “/data/app/com.GameKing.HabNochNie-L3MIBybEpvMaDBB1n2xvSQ==/base.apk”],nativeLibraryDirectories=[/data/app/com.GameKing.HabNochNie-L3MIBybEpvMaDBB1n2xvSQ==/lib/arm, /data/app/com.GameKing.HabNochNie-L3MIBybEpvMaDBB1n2xvSQ==/base.apk!/lib/armeabi-v7a, /system/lib, /system/vendor/lib]]
at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:93)
at java.lang.ClassLoader.loadClass(ClassLoader.java:379)
at java.lang.ClassLoader.loadClass(ClassLoader.java:312)
… 9 more
at UnityEngine.AndroidJNISafe.CheckException () [0x00091] in <07e4b01d268e49d9893add5a5bf8a7f1>:0
at UnityEngine.AndroidJNISafe.CallStaticObjectMethod (System.IntPtr clazz, System.IntPtr methodID, UnityEngine.jvalue[ ] args) [0x00011] in <07e4b01d268e49d9893add5a5bf8a7f1>:0
at UnityEngine.AndroidJavaObject._CallStatic[ReturnType] (System.String methodName, System.Object[ ] args) [0x002d6] in <07e4b01d268e49d9893add5a5bf8a7f1>:0
at UnityEngine.AndroidJavaObject.CallStatic[ReturnType] (System.String methodName, System.Object[ ] args) [0x00001] in <07e4b01d268e49d9893add5a5bf8a7f1>:0
at UnityEngine.AndroidJavaObject.FindClass (System.String name) [0x0001d] in <07e4b01d268e49d9893add5a5bf8a7f1>:0
at UnityEngine.AndroidJavaClass._AndroidJavaClass (System.String className) [0x00012] in <07e4b01d268e49d9893add5a5bf8a7f1>:0
at UnityEngine.AndroidJavaClass…ctor (System.String className) [0x00007] in <07e4b01d268e49d9893add5a5bf8a7f1>:0
at UnityEngine.AndroidJavaProxy…ctor (System.String javaInterface) [0x00000] in <07e4b01d268e49d9893add5a5bf8a7f1>:0
at UnityEngine.Advertisements.Platform…ctor () [0x00000] in :0
at UnityEngine.Advertisements.Creator.CreatePlatform () [0x00000] in :0
UnityEngine.DebugLogHandler:Internal_LogException(Exception, Object)
UnityEngine.DebugLogHandler:LogException(Exception, Object)
UnityEngine.Logger:LogException(Exception, Object)
UnityEngine.Debug:LogException(Exception)
UnityEngine.Advertisements.Creator:CreatePlatform()
UnityEngine.Advertisements.Advertisement:.cctor()
UnityBanner:Start() (at C:\Users\Joshua\Documents\IchHabNochNie\Assets\Scripts\UnityBanner.cs:22)

Hello,
It looks like something is wrong with your implementation. You can look for the code samples here:
https://unityads.unity3d.com/help/unity/integration-guide-unity