Feed him diuretic food. Not just dog food.

Give him chopped water melon skin( put in the freezer first)or radishes, with every meal. Also should add the drinking water to each meal. Lest get kidney problem. He needs to pee 5 times a day with decent quantity. And you feed him twice a day, but he needs to poop 4 time a day. That 's too much. Maybe the meal too big. You can feed him less.