Hello Com,
i wanna copie and paste stuff from GTA 5 to UE4, cause i wanna know which Dimensions they used for the character, houses and cars.

Thank you guys.

That’s not legal–if you want at house you will have to buy/make one yourself.

I’ve imported the DOOM marine model in 3ds max not long ago (from latest doom game). You probably need a special software for that. Check out on gta5 modding sites for a file extracter or something like that. (OpenIV maybe?)
Don’t use the assets for commercial projects like darthviper said but I would not be too scared to play with assets for personal project/learning.