>>150099759
Since there's only one break (unless it's really hot, then there's an additional short drinking break per half), the manager/coach cannot do a lot when the game is underway. All he can do is shout inputs and hope the players will follow. Maybe he has the chance to have a longer (a few seconds) talk with individual players, especially the players on the wing on the side of the bench. They usually shout/say a lot, but the extent to which that stuff is followed is questionable
Of course, the clubs have entire staffs of coaches. There are video analysts following the game on TV as well, there are specific coaches (set pieces, athletic, etc). And they all give the main manager their input. Together, they coordinate what to do in the halftime address, and they delegate other tasks, like sending players to warm-up
Of course, most of the work happens pre-game