Is there a way to open maps into gtk radiant for example siwa oasis. if there is please tell me. Thank you 
Opening Maps
tristar2002
(tristar2002)
#1
Pytox
(Pytox)
#2
If you want to open a map like that you will need to decompile them and change everything but that’s actually against the rules. The only official map you can open is goldrush .
kamikazee
(kamikazee)
#3
Decompiling isn’t against the rules, only using the decompiled map without permission is against them.
kamikazee
(kamikazee)
#5
Models don’t need decompiling, you just open them.
I think what you’re pointing to are misc_models. Here the models get compiled into the map so no seperate model files need to be supplied with the map. And you are right, those cannot be recovered.