How to upgrade version of Android app project for Sunmi V2 device?

Question

I don't know aboutupgrading of Sunmi app project SDK upgrading? or device upgrading? How to compile this project? How can I use what emulator? This is bundle.gradle code

apply plugin: 'com.android.library'

android {
    compileSdkVersion 28
    buildToolsVersion "28.0.3"

    defaultConfig {
        minSdkVersion 21
        targetSdkVersion 26
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"

    }


    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }


    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }

}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])

    implementation 'androidx.appcompat:appcompat:1.1.0'
    testImplementation 'junit:junit:4.12'
    testImplementation "com.google.truth:truth:1.0"
}

How to upgrade this app? Thank you so much if you provide me detailed roadmap.