Fail building flutter app with firebase for android emulator

I've tried multiple solutions online for hours and it just doesn't work :(

The error is like super long and one of them is like:

Could not resolve all files for configuration ':app:classpath'. > Could not find com.google.flatbuffers:flatbuffers-java:1.12.0.

My build.gradle in the app file looks like:

def localProperties = new Properties()
def localPropertiesFile = rootProject.file('local.properties')
if (localPropertiesFile.exists()) {
    localPropertiesFile.withReader('UTF-8') { reader ->
        localProperties.load(reader)
    }
}

def flutterRoot = localProperties.getProperty('flutter.sdk')
if (flutterRoot == null) {
    throw new GradleException("Flutter SDK not found. Define location with flutter.sdk in the local.properties file.")
}

def flutterVersionCode = localProperties.getProperty('flutter.versionCode')
if (flutterVersionCode == null) {
    flutterVersionCode = '1'
}

def flutterVersionName = localProperties.getProperty('flutter.versionName')
if (flutterVersionName == null) {
    flutterVersionName = '1.0'
}

apply plugin: 'com.android.application'
apply plugin: 'kotlin-android'
apply plugin: 'com.google.gms.google-services'
apply from: "$flutterRoot/packages/flutter_tools/gradle/flutter.gradle"

android {
    compileSdkVersion flutter.compileSdkVersion
    ndkVersion flutter.ndkVersion

    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }

    kotlinOptions {
        jvmTarget = '1.8'
    }

    sourceSets {
        main.java.srcDirs += 'src/main/kotlin'
    }

    defaultConfig {
        // TODO: Specify your own unique Application ID (https://developer.android.com/studio/build/application-id.html).
        applicationId "com.example.stybyc"
        minSdkVersion 19 //*** This is the part that needs to be changed, previously was 16
        targetSdkVersion 28
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
        multiDexEnabled true
    }

    buildTypes {
        release {
            // TODO: Add your own signing config for the release build.
            // Signing with the debug keys for now, so `flutter run --release` works.
            signingConfig signingConfigs.debug
        }
    }
}

flutter {
    source '../..'
}

repositories {
    // Check that you have the following line (if not, add it):
    google()  // Google's Maven repository
    mavenCentral()
    //maven { url 'https://plugins.gradle.org/m2/'}

}

dependencies {
    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
    implementation 'com.android.support:multidex:1.0.3'
    implementation platform('com.google.firebase:firebase-bom:30.1.0')
    classpath 'com.android.tools.build:gradle:4.2.0'
    classpath 'com.google.gms:google-services:4.3.5'
    classpath 'com.google.firebase:firebase-crashlytics-gradle:2.6.0'
    classpath 'com.google.firebase:perf-plugin:1.4.0'

    //firebase
    implementation 'com.google.firebase:firebase-ads:20.1.0'
    implementation 'com.google.firebase:firebase-core:19.0.0'
    implementation 'com.google.firebase:firebase-crash:16.2.1'
    implementation 'com.google.firebase:firebase-messaging:22.0.0'
    implementation 'com.firebase:firebase-jobdispatcher:0.8.5'
    implementation 'com.google.firebase:firebase-auth:21.0.0'
    implementation 'com.google.firebase:firebase-firestore:23.0.0'
}

buildscript {
    repositories {
        google()
        //... others
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:4.2.0'
        classpath 'com.google.gms:google-services:4.3.5'

        // others...
    }
}

and my build.gradle for the project looks like

buildscript {
    ext.kotlin_version = '1.6.10'
    repositories {
        google()
        mavenCentral()
    }

    dependencies {
        classpath 'com.android.tools.build:gradle:7.1.2'
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
        classpath 'com.google.gms:google-services:4.3.8'
    }
}

allprojects {
    repositories {
        google()
        mavenCentral()
    }
}

rootProject.buildDir = '../build'
subprojects {
    project.buildDir = "${rootProject.buildDir}/${project.name}"
}
subprojects {
    project.evaluationDependsOn(':app')
}

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