doom 2 hell on earth modding error

[The Dark Angel]

well i was making my first doom 2 mod then suddenly when i open my WAD file with slumped i see this:
   

my wad first looked like:
   

PLEASE HELP OMG I PANICKING I DONT WANT TO START OVER I WORKED VERY HARD FOR IT I WORKED 3 MONTHS AND IT WASN'T EVEN FINISHED.