ANDROID ERROR “Execution failed for task ” com.android.build.api.transform.TransformException:

I can not run my project, I always try to get the following error

Error:Execution failed for task ‘:app:transformClassesWithJarMergingForDebug’.
com.android.build.api.transform.TransformException: java.util.zip.ZipException: duplicate entry: com/google/android/gms/internal/zzam.class

My settings are:
compileSdkVersion 26
buildToolsVersion “26.0.2”
minSdkVersion 15
targetSdkVersion 26

This is my Gradle file complete:

apply plugin: 'com.android.application'

android {
    compileSdkVersion 26
    buildToolsVersion "26.0.2"
    defaultConfig {
        applicationId "com.seriesflixapp.imperioflixapp"
        manifestPlaceholders = [onesignal_app_id               : "xxxxxx",
                                // Project number pulled from dashboard, local value is ignored.
                                onesignal_google_project_number: "xxxxxxx"]
        minSdkVersion 15
        targetSdkVersion 26
        versionCode 3
        versionName "2.1"
        multiDexEnabled true
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    compile fileTree(include: ['*.jar'], dir: 'libs')
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    // OneSignal SDK
    compile 'com.android.support:appcompat-v7:26.0.2'
    compile 'com.android.support:design:26.0.2'
    compile 'com.google.firebase:firebase-ads:10.2.0'
    compile 'com.google.firebase:firebase-messaging:10.2.0'
    compile 'com.onesignal:OneSignal:3.6.0'
    compile fileTree(include: '*.jar', dir: 'libs')
    compile 'com.android.support.constraint:constraint-layout:1.0.2'
    testCompile 'junit:junit:4.12'
}


apply plugin: 'com.google.gms.google-services'

This is my OTHER Gradle file():

// Top-level build file where you can add configuration options common to all sub-projects/modules.

buildscript {
    repositories {
        jcenter()

    }
    dependencies {
        classpath 'com.android.tools.build:gradle:2.3.3'
        classpath 'com.google.gms:google-services:3.0.0'

        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
}

allprojects {
    repositories {
        jcenter()
        maven{
            url "https://maven.google.com"
        }
    }
}

task clean(type: Delete) {
    delete rootProject.buildDir
}

my dependencies
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