Weight loss comes from eating less calories than your body needs. If a 90 kg man needs 3000 calories to maintain his fat then he needs to eat 2800 calories to lose around 0.2 kilograms a week.
The most commonly used method is to eat 200-500 calories less than needed.
Progressive overload is the name of the game
The body builds bigger muscle to withstand stress, bigger stress=bigger muscles. If your muscles are not growing then try increasing the sets,repetitions,weight,speed,time under tension or the rest between sets.
Since you asked about which rep range to do, The truth is that it really doesn't matter for muscle building. Low reps build strength and muscle while high reps build endurance and muscle, it all comes down to preference.
Biological law of accommodation
If you keep giving your body the same type of stress over and over again you will eventually plateau in all senses be it endurance,muscle building or strength, once you plateau if you don't implement any kind of Periodization you will totally stall or worse become weaker and lose muscles because the body no more adapts to stress but ''accommodates'' itself to stress.
People who never did any physical activity in their entire life might be able to train for 1 or 2 years without experiencing any stall.
Keep changing exercises every 2-3 weeks and use a variety of exercises to avoid plateaus.
Example : Bench press> Weighted dips> Weighted push up> Repeat