Adding FCM to existing Ionic project - need help

I already have Ionic project that works on Android/iOS and need to add Push Notifications there.

some dependencies from package.json:

    "@ionic-native/core": "^5.18.0",
    "@ionic/angular": "^4.11.7",
    "caniuse-lite": "^1.0.30001016",
    "cordova-android": "^8.1.0",
    "cordova-browser": "^6.0.0",
    "cordova-ios": "^5.1.1",
    "firebase": "^7.24.0",
    "ionic-native": "^2.9.0",

and info :

Ionic:
   Ionic CLI                     : 6.12.4 (/home/user/.nvm/versions/node/v10.18.0/lib/node_modules/@ionic/cli)
   Ionic Framework               : @ionic/angular 4.11.7
   @angular-devkit/build-angular : 0.801.3
   @angular-devkit/schematics    : 8.1.3
   @angular/cli                  : 8.1.3
   @ionic/angular-toolkit        : 2.1.1
Cordova:
   Cordova CLI       : 10.0.0
   Cordova Platforms : android 8.1.0
   Cordova Plugins   : cordova-plugin-ionic-webview 4.1.3, (and 9 other plugins)
Utility:
   cordova-res : not installed
   native-run  : 1.3.0

Android project.properties:

target=android-28
android.library.reference.1=CordovaLib
android.library.reference.2=app
cordova.system.library.1=com.android.support:support-v4:27.+
cordova.system.library.2=com.android.support:support-annotations:27.+
cordova.gradle.include.1=cordova-plugin-fcm-with-dependecy-updated/projectname-FCMPlugin.gradle

\app\buid.gradle\

apply plugin: 'com.android.application'

buildscript {
    repositories {
        mavenCentral()
        google()
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:3.3.0'
    }
}
allprojects {
    repositories {
        mavenCentral()
        jcenter()
    }
}
task wrapper(type: Wrapper) {
    gradleVersion = '4.10.3'
}
...

ProjectBuilder.js:

var distributionUrl = process.env['CORDOVA_ANDROID_GRADLE_DISTRIBUTION_URL'] || 'https\\://services.gradle.org/distributions/gradle-4.10.3-all.zip';

In Firebase console I have added Android project and donwload google-services.json to project root, then

ionic cordova plugin add cordova-plugin-fcm-with-dependecy-updated

As state in some guides for adding FCM into ionic project there also need add ionic-native/fcm:

npm install @ionic-native/fcm

but here GitHub - andrehtissot/cordova-plugin-fcm-with-dependecy-updated: Google FCM Push Notifications Cordova Plugin script for uninstall this:

npm uninstall @ionic-native/fcm # Ionic support is included and conflicts with @ionic-native's implementation.

So I’m trying with and w/o the ionic-native/fcm

now I have:

> cordova build android --device
[cordova] 
[cordova] FAILURE: Build failed with an exception.
[cordova] 
[cordova] * What went wrong:
[cordova] A problem occurred configuring project ':app'.
[cordova] > Could not create task ':app:processDebugGoogleServices'.
[cordova]    > Cannot create a proxy class for abstract class 'GoogleServicesTask'.
...

any help/suggestions would be appreciated!