what do you mean by this?

building muscle and lose belly fat is kinda of an oxymoron. Though from experience, this kind of body recomposition is technically possible especially for someone who just started strength training. but the ratio of muscle build:fat loss will not be what you're expecting. The likely scenario, you'll lose abit of fat, gained some muscle and your strength gain progress will stall.

Pick 1 side of either coin. lose the body fat, calorie deficit you shall be in.

increase muscle, caloric surplus. This is the most efficient way to see progress.

well honestly speaking, only you yourself can decide on this part. lol

Though if i am in your situation, this will be what i'd do (since you're doing stronglift), and it comes down to the 3 main lifts.

If your bench, squat and deadlift are currently lower than your current bodyweight (i.e you weight 70kg but benches only 50kg), i'd go for very slight bulk (around 100-200 tops calorie surplus) to gain some strength and muscle before cutting.

If they're well above or at least your bodyweight, then i'll start cutting.

honestly, no point cutting when you're lifting low weight as you'll look pretty bad after the fat's gone (as you'll hardly have any muscle left).