Restoring its factory settings

I'll start by describing myself, but those who aren't interested can skip this: I'm white, 1.68m (short, I know). When I was training, I was a relatively muscular guy for a natural physique, but for some reason I stopped going to the gym a few months ago and I'm doing calisthenics now, which hasn't helped me maintain as much muscle mass and has given me a slight beer belly on weekends, lol. Nothing too serious, but I don't have defined abs anymore and I'm what people here call a "galego" (fair-skinned), I have lighter hair, though not completely blonde.