Your btrfs was in a LUKS partition and you can decode it? But know that btrfs uses smart compression by default, so you can recover jpeg or zip easily in general, but for stuff compressed, not sure how to decompress them by hand … Like other commenter wrote, first do a full copy on another HD.

Probably depends a lot on what options you had enabled on BTRFS. Metadata (i.e. what files are stored where) is normally replicated so you may be able to rebuild the information.

Step 1 is always to copy the filesystem somewhere else, and then work on the copy. That way, if you screw up, you can always make a new copy and start over. Don’t write anything to the drive you’re trying to fix. Always work on the copy. In fact, once you’ve made the copy, disconnect the original.