My dog doesn’t go to toilet other than my garden (will be a problem when I move)

My swiss sheperd (10 months) doesn't pee or poo other than in the garden. If I go out in the wild, or other places where other dogs have been, or where no dogs go, he for some reason doesn't get the instinct to pee or poo like the others.

I'm planning to move him to my apartment in the summer, and this will definitively become a problem… I read that when you change house, you have to re-train him. But my worry is that like this, I can't take him anywhere outside for very long because he doesn't do his things even for fun.