Hello,
I have painted the wrong area of the map editor and destroyed a previously made level. Luckily I do have a backup of an older file. How do I copy a 16x16 map editor area from one cart to another cart ?

Easy way: open up both .p8 files in your favorite text editor, find the map section, and copy/paste accordingly. The data is laid out in the same order as you'd see it in the map editor; you'll want to be careful (and make backups of both carts before you begin!) but this should do the trick.

that worked thank you