Android studio :connection timed out

apply plugin: 'com.android.application'

android {
    compileSdkVersion 28
    defaultConfig {

        applicationId "tn.tunisapp.rawabimobile"
        minSdkVersion 15
        targetSdkVersion 28
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
        
        // paramètres proxy
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'com.android.support:appcompat-v7:28.0.0-rc02'
    implementation 'com.android.support.constraint:constraint-layout:1.1.2'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.2'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
}

Executing tasks: [assemble]

Configuration on demand is an incubating feature.

FAILURE: Build failed with an exception.

 What went wrong:A problem occurred configuring root project 'RawabiMobile'.> Could not resolve all artifacts for configuration ':classpath'.   > Could not download builder.jar (com.android.tools.build:builder:3.1.4)      > Could not get resource 'https://dl.google.com/dl/android/maven2/com/android/tools/build/builder/3.1.4/builder-3.1.4.jar'.         > Could not GET 'https://dl.google.com/dl/android/maven2/com/android/tools/build/builder/3.1.4/builder-3.1.4.jar'. Received status code 407 from server: Proxy Authentication Required   > Could not download lint-gradle-api.jar (com.android.tools.lint:lint-gradle-api:26.1.4).....     > Could not get resource 'https://jcenter.bintray.com/org/glassfish/jaxb/txw2/2.2.11/txw2-2.2.11.jar'.         > Could not GET 'https://jcenter.bintray.com/org/glassfish/jaxb/txw2/2.2.11/txw2-2.2.11.jar'. Received status code 407 from server: Proxy Authentication Required   > Could not download istack-commons-runtime.jar (com.sun.istack:istack-commons-runtime:2.21)      > Could not get resource 'https://jcenter.bintray.com/com/sun/istack/istack-commons-runtime/2.21/istack-commons-runtime-2.21.jar'.         > Could not GET 'https://jcenter.bintray.com/com/sun/istack/istack-commons-runtime/2.21/istack-commons-runtime-2.21.jar'. Received status code 407 from server: Proxy Authentication Required* 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://gradle.org/help/BUILD FAILED in 0s