First I tried apps like APK Explorer and APK Editor. APK Explorer worked, but I doubt that the apk package works for other mobiles than your own. APK Editor did not seem to work, unless you buy Pro version. Android Studio is difficult and complex to use.
Simplest is to use a PC and download Apktool and a wrapper script and install it. Make a folder where you put the apk-file that shall be edited. In the Power Shell in that folder write the command: apktool d nameofyourapk Now the apk is unpacked and I could edit files with Notepad++
Then its time to create an apk package and in the command window write: apktool build folderforeditedapkfile.
Now this apk-package must be signed. This is complex if you use Android Studio or follows other descriptions.
The simple solution is to download Uber Apk Signer and then change the name to: uber-apk-signer. Then copy this program to the identical folder as the apk that shall be signed: java -jar uber-apk-signer.jar --apks /path/to/apks The signing takes a few seconds and a new signed apk is found in the directory with a new name. These two programs has worked flawlessly and is extremely simple and fast to use compared with Android Studio.