Getting could not resolve all artifact error at application run

Recently after upgrading android studio 4.1 my app started to stuck in "running gradle task assembledebug" so i checked the web for possible solution Tried flutter clean and gradle commands changed gradle files but nothing worked finally deleted gradle and reinstalled android studio again but now i can't get android sdk 28 to be installed (it doesnt appear in sdk list) so i changed sdk to 29 but whenever i try to run my app it gives the fallowing errors

FAILURE: Build failed with an exception.

* What went wrong:
A problem occurred configuring root project 'android'.
> Could not resolve all artifacts for configuration ':classpath'.
   > Could not resolve com.android.tools.build:gradle:3.5.3.
     Required by:
         project :
      > Could not resolve com.android.tools.build:gradle:3.5.3.
         > Could not get resource 'https://dl.google.com/dl/android/maven2/com/android/tools/build/gradle/3.5.3/gradle-3.5.3.pom'.
            > Could not GET 'https://dl.google.com/dl/android/maven2/com/android/tools/build/gradle/3.5.3/gradle-3.5.3.pom'.
               > Connect to localhost:3128 [localhost/127.0.0.1, localhost/0:0:0:0:0:0:0:1] failed: Connection refused: connect
      > Could not resolve com.android.tools.build:gradle:3.5.3.
         > Could not get resource 'https://jcenter.bintray.com/com/android/tools/build/gradle/3.5.3/gradle-3.5.3.pom'.
            > Could not GET 'https://jcenter.bintray.com/com/android/tools/build/gradle/3.5.3/gradle-3.5.3.pom'.
               > Connect to localhost:3128 [localhost/127.0.0.1, localhost/0:0:0:0:0:0:0:1] failed: Connection refused: connect
   > Could not resolve com.google.gms:google-services:4.3.4.
     Required by:
         project :
      > Could not resolve com.google.gms:google-services:4.3.4.
         > Could not get resource 'https://dl.google.com/dl/android/maven2/com/google/gms/google-services/4.3.4/google-services-4.3.4.pom'.
            > Could not GET 'https://dl.google.com/dl/android/maven2/com/google/gms/google-services/4.3.4/google-services-4.3.4.pom'.
               > Connect to localhost:3128 [localhost/127.0.0.1, localhost/0:0:0:0:0:0:0:1] failed: Connection refused: connect
      > Could not resolve com.google.gms:google-services:4.3.4.
         > Could not get resource 'https://jcenter.bintray.com/com/google/gms/google-services/4.3.4/google-services-4.3.4.pom'.
            > Could not GET 'https://jcenter.bintray.com/com/google/gms/google-services/4.3.4/google-services-4.3.4.pom'.
               > Connect to localhost:3128 [localhost/127.0.0.1, localhost/0:0:0:0:0:0:0:1] failed: Connection refused: connect

* Try:
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* Get more help at https://help.gradle.org

BU�LD FAILED in 1m 24s
Exception: Gradle task assembleDebug failed with exit code 1

My current project level build gradle file is like this.

buildscript {
    repositories {
        google()
        jcenter()
    }

    dependencies {
        classpath 'com.android.tools.build:gradle:3.5.3'
        classpath 'com.google.gms:google-services:4.3.4'
    }
}

allprojects {
    repositories {
        google()
        jcenter()
    }
}

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

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

App lvl build gradle file is like this:

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 from: "$flutterRoot/packages/flutter_tools/gradle/flutter.gradle"

android {
    compileSdkVersion 29

    lintOptions {
        disable 'InvalidPackage'
    }

    defaultConfig {
        // TODO: Specify your own unique Application ID (https://developer.android.com/studio/build/application-id.html).
        applicationId "com.farukdurusoy.sayi_avi"
        minSdkVersion 16
        targetSdkVersion 29
        versionCode flutterVersionCode.toInteger()
        versionName flutterVersionName
        testInstrumentationRunner "androidx.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 '../..'
}

dependencies {
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'androidx.test:runner:1.1.1'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.1.1'
}

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

Also disabled my firewalls. Any suggestions?