Lay your restaurant our with tables for 4, 6 and 8 diners. If you do not want all the groups then delete the group file or only lay your restaurant out with the tables you require.

I have made this restaurant mod due to the frustrations of the Sims 4 Restaurants behaviours, this will improve staff and customers. 0, 3, 5-star restaurant at the start (and 5 stars with no changes to the settings)

Maxed Skills will make sure all your staff that you hire for restaurant, vet or retail are at their highest skills so no need for training.