How to change the Gradle build to an earlier version ( android studio )?

Question

I’m creating a project that runs on android studio version 3.1, and I have this old version of android studio but the build Gradle is updated and I can’t make my codes run I don’t want to change my codes or adapt I just want to go back to old version can anyone help me ? I tried to give up home and install again and still does not change anything in build.Radle .

like this now

android {
compileSdkVersion 28
defaultConfig {
    applicationId "com.example.t_gamer.myapplication"
    minSdkVersion 16
    targetSdkVersion 28
    versionCode 1
    versionName "1.0"
    testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
}
buildTypes {
    release {
        minifyEnabled false
        proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
    }

how I want it to stay

android {
compileSdkVersion 27
defaultConfig {
    applicationId "com.example.t_gamer.deepcooeesite"
    minSdkVersion 16
    targetSdkVersion 27
    versionCode 1
    versionName "1.0"
    testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
}
buildTypes {
    release {
        minifyEnabled false
        proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
    }
}
productFlavors {
}