Need Help Fixing A Crash in an Android E-Commerce App and copying it as a new/different app

Hi there. I have an E-Commerce App that I want to copy and add new designs and name to be another app. I also want to fix a crash in the app first and make sure there are no other major crashing issues with it - because we haven't update it in a long time.

Note: My normal developer who is sick can usually copy these in 30 minutes. I always give him images that are the same name to replace the designs.

Thanks!