I just bought the game today and the game crash every 3 - 4 minutes whe I start a mission, is there a way to fix the crashing problems?

from my years of experience with gog games, i can only recommend to not buy games from gog, except from very few titles. especially if its old games. gog sells games and doesn't care at all if they work. since you just bought rtcw, try to refund it or do a credit card chargeback. and then buy the game elsewhere.

There is a support section for the game:
https://support.gog.com/hc/en-us/articles/214074445-Return-to-Castle-Wolfenstein?product=gog

You can also check the specific forum for that game:
https://www.gog.com/forum/wolfenstein_series#1628628642

And if you do not find the solution, then contact support with your problem (I think that you have a link in the support section)

https://www.gog.com/forum/wolfenstein_series/return_to_castle_wolfenstein_unofficial_patch/page1

Thank you very much for the unnoficial patch it seems to be solved now, thanks again.

Whilst on the subject you may want to look at these mods as they add a lot to the game such as better resolutions and better graphics and some content:
https://www.moddb.com/mods/realrtcw-realism-mod
https://www.moddb.com/mods/rtcw-venom-mod

I can see you got it fixed.

Out of interest, are you using onboard graphics?

Mainly asking because I saw that it doesn't support them on the store page. I was going to try on my laptop, but ended up playing through RTCW on my desktop last month (with discrete graphics card) and it seemed to work fine (apart from some weird physics type bug with the loper enemies who were much faster than I remembered and jerkier in their movements). This was without any third party patches.

Played it on a laptop with an intel hd myself. Needed the unnofical patch to get it going but was fine after that.

https://www.gog.com/forum/wolfenstein_series/iortcw_installation_instructions