GTA 5 is a game that will have your eyes stuck to the screen, and really there is only one way you’re going to complete the game, with sheer determination. It’s a more difficult than the previous GTA games, and because of this it can take a significantly larger amount of time.
There are various question mark missions which are practically extras and if you want to complete the game quickly and by game we mean the story, then you should leave these, because they are actually not significant, only the mission with letters are important.
Spend less time getting haircuts, changing outfits, switching cars and attracting police, because these can divert you away from the missions, meaning you’re bound to take longer to complete it.