Change Minimum API Level of Android Studio Project

You do not have to create a new project for changing that. You only have to adjust the minimum SDK Version that is defined in the file "build.gradle (Module:app)" of your project. After opening your project in Android Studio, you will find that file in the tree structure on the left of the main window under "Gradle Scripts".

In this file, you will find something like that:

...

android {
    compileSdkVersion 29
    buildToolsVersion "29.0.2"
    defaultConfig {
        applicationId "com.example.myapp"
        minSdkVersion 15
        targetSdkVersion 29
        versionCode 1
        versionName "1.0"
        ...
    }
    ...
}

...

Now, you can just change the value behind minSdkVersion to the API level you want.

Alternatively you can change the level in the menu File > Project Structure > Modules > Default Config > Min SDK Version.
2020-10-17 at 22:20