react-native build error: Could not find method implementation() for arguments [jscFlavor] on project ':app' of type org.gradle.api.Project

I have kept android emulator running.

This is the error I get when I run react-native run-android :

error Failed to install the app. Make sure you have the Android development environment set up: https://facebook.github.io/react-native/docs/getting-started.html#android-development-environment. Run CLI with --verbose flag for more details. Error: Command failed: ./gradlew app:installDebug -PreactNativeDevServerPort=8081

FAILURE: Build failed with an exception.

• Where: Build file '/Users/yashatreya/Desktop/Realyze/Realyze/android/app/build.gradle' line: 209

• What went wrong:

A problem occurred evaluating project ':app'.

Could not find method implementation() for arguments [org.webkit:android-jsc:+] on project ':app' of type org.gradle.api.Project.

• Try: Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.

• Get more help at https://help.gradle.org

This is my app/build.gradle:

apply plugin: "com.android.application"
import com.android.build.OutputFile

project.ext.react = [
    entryFile: "index.js",
    enableHermes: false,  // clean and rebuild if changing
]

apply from: "../../node_modules/react-native/react.gradle"

def enableSeparateBuildPerCPUArchitecture = false


def enableProguardInReleaseBuilds = false

def jscFlavor = 'org.webkit:android-jsc:+' // Error seems to be coming from here, as displayed in the error message

def enableHermes = project.ext.react.get("enableHermes", false);

android {
    compileSdkVersion rootProject.ext.compileSdkVersion

    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }

    defaultConfig {
        applicationId "com.realyze"
        minSdkVersion 21 
        targetSdkVersion rootProject.ext.targetSdkVersion
        versionCode 1
        versionName "1.0"
        multiDexEnabled true

    }
    // rootProject.ext.minSdkVersion
    splits {
        abi {
            reset()
            enable enableSeparateBuildPerCPUArchitecture
            universalApk false  // If true, also generate a universal APK
            include "armeabi-v7a", "x86", "arm64-v8a", "x86_64"
        }
    }
    signingConfigs {
        debug {
            storeFile file('debug.keystore')
            storePassword 'android'
            keyAlias 'androiddebugkey'
            keyPassword 'android'
        }
    }
    buildTypes {
        debug {
            signingConfig signingConfigs.debug
        }
        release {
            // Caution! In production, you need to generate your own keystore file.
            // see https://facebook.github.io/react-native/docs/signed-apk-android.
            signingConfig signingConfigs.debug
            minifyEnabled enableProguardInReleaseBuilds
            proguardFiles getDefaultProguardFile("proguard-android.txt"), "proguard-rules.pro"
        }
    }
    // applicationVariants are e.g. debug, release
    applicationVariants.all { variant ->
        variant.outputs.each { output ->
            // For each separate APK per architecture, set a unique version code as described here:
            // https://developer.android.com/studio/build/configure-apk-splits.html
            def versionCodes = ["armeabi-v7a": 1, "x86": 2, "arm64-v8a": 3, "x86_64": 4]
            def abi = output.getFilter(OutputFile.ABI)
            if (abi != null) {  // null for the universal-debug, universal-release variants
                output.versionCodeOverride =
                        versionCodes.get(abi) * 1048576 + defaultConfig.versionCode
            }

        }
    }
}

dependencies {
    implementation project(':react-native-sound')
    implementation project(':react-native-audio')
    implementation 'com.android.support:multidex:2.0.1'
    // implementation project(':@react-native-community_datetimepicker')
    implementation project(':react-native-gesture-handler')
    implementation fileTree(dir: "libs", include: ["*.jar"])
    implementation "com.facebook.react:react-native:+"  // From node_modules
    implementation 'androidx.appcompat:appcompat:1.1.0-rc01'
    implementation 'androidx.swiperefreshlayout:swiperefreshlayout:1.1.0-alpha02'
    implementation 'com.google.firebase:firebase-analytics:17.2.0'
    implementation 'com.google.firebase:firebase-auth:19.1.0'
    implementation project(path: ":@react-native-firebase_auth")
    implementation project(path: ":@react-native-firebase_messaging")
    implementation project(path: ":@react-native-firebase_database")
    implementation project(':react-native-datetimepicker')
    implementation project(path: ":@react-native-firebase_firestore")
    implementation project(path: ":@react-native-firebase_functions")
}

    if (enableHermes) {
        def hermesPath = "../../node_modules/hermes-engine/android/";
        debugImplementation files(hermesPath + "hermes-debug.aar")
        releaseImplementation files(hermesPath + "hermes-release.aar")
    } else {
        implementation jscFlavor //error points to this line.
    }
// }

// Run this once to be able to run the application with BUCK
// puts all compile dependencies into folder libs for BUCK to use
task copyDownloadableDepsToLibs(type: Copy) {
    from configurations.compile
    into 'libs'
}

apply from: file("../../node_modules/@react-native-community/cli-platform-android/native_modules.gradle"); applyNativeModulesAppBuildGradle(project)
apply plugin: 'com.google.gms.google-services'

This is the root build.gradle:

buildscript {
    ext {
        buildToolsVersion = "28.0.3"
        minSdkVersion = 16
        compileSdkVersion = 28
        targetSdkVersion = 28
    }
    repositories {
        google()
        jcenter()
    }
    dependencies {
        classpath "com.android.tools.build:gradle:3.4.2"
        classpath 'com.google.gms:google-services:4.3.2'

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

allprojects {
    repositories {
        mavenLocal()
        maven {
            // All of React Native (JS, Obj-C sources, Android binaries) is installed from npm
            url("$rootDir/../node_modules/react-native/android")
        }
        maven {
            // Android JSC is installed from npm
            url("$rootDir/../node_modules/jsc-android/dist")
        }

        google()
        jcenter()
        maven { url 'https://jitpack.io' }
    }
}

I am trying to solve this error since a week now, please help me. Thank you