Quick Update
Just to let you guys know, after trying to downgrade the graphics from medium to low and a bunch of other possibilities, i've tried uninstalling and then reinstalling the game and it actually worked. I've been playing in low and then in medium graphics for the whole afternoon and not a crash or freeze until now.
I'm not sure, but i guess that it could be some how related to the shaders cache? Because those have been updated after reinstallation and i've seen in other forums that deleting the shaders have worked in similar cases.