You need a apk editor. And download Manual File. After you open the apk editor, follow this step:
1. Choose the "Select apk file"
2. Search you're apk file
3. click that and choose simple edit.
4. Replace the file example: "sharedassets18.assets.split0 (make sure it's the same file so it won't broken the game)
5. After you replace the file select save.
6. Select The Apk file again (it saved at Apk Editor file) then click the apk file ( it should be "gen_signed.apk") after that click the common edit then click the target SDK. Then change it to 29, (also you can change the apk icon. Make sure it's ".png"
7. Click save and done