I am joining a gym, I really only want to loose weight (expressly in my belly and chin area)

For me it took a full 6 months of intermittent fasting along with 40 + hr fasts, bodyweight exercise and then cardio to see any significant loss.

Anyone trying to lose weight should plan for minimum 6months time frame. You won't see results for at least 3 months.
Get a digital scale and track ur water weight so UK when you're actually losing fat.