We, the French, enjoy taking our time to taste the food and appreciate our company, it will not be rare to spend two or three hours dining.
In any French restaurant (except fast food), do not expect to eat in less than 40 minutes - up to 1hr minimum if you take a 3 course meal.
If you don't want to spend too much time eating, while entering a brasserie or bistro - before being sitted - you may tell the waiter that you only have 40 min / 1hr....to eat and ask him if this is ok.
If you book at a gastronomic, star rated restaurant, plan to be at the table for at least 2h30 - 3hrs and it can be more in the 2 or 3 star rated Michelin restaurants.
Bon Appétit !