A BMW M5 F10 already exists as an add on car, here is the link:
https://www.gta5-mods.com/vehicles/bmw-m5-f10-2012-add-on-tunable-autovista
Also if you download this you might want to use this taillight fix:
https://www.gta5-mods.com/paintjobs/bmw-m5-f10-autovista-taillight-fix
Have a nice day 
