Look in the backdrop code for instructions if you don't really understand. Please look at the original project @Zocker_tutor made for further instructions.
For a bit of more simpleness, I added an ask block and edited it a bit, so you don't have to edit the code lol, it took me some time, and I gave up but when I looked at the code on this project https://scratch.mit.edu/projects/994434176 It helped me and I was able to release the project! (Project started being made in March 31)