...
android {
    compileSdkVersion 28 // Use latest version
    buildToolsVersion "28.0.3" // Latest version
...

...
dependencies {
    compile fileTree(dir: "libs", include: ["*.jar"])
    compile "com.android.support:appcompat-v7:28.+" // Use latest version
    implementation "com.facebook.react:react-native:+"  // use 'implementation' instead of compile
    implementation project(':react-native-image-picker')
    implementation project(':react-native-background-fetch')
    implementation project(':react-native-push-notification')
....