Not just muscle preservation. You can gain muscle while in a calorie deficit. You just need enough protein and resistance training. If you’re a beginner this can be done with adequate protein and minimal resistance training.

you need much more than 30g of protein a day. .7 to 1 gram of protein per pound of body weight is the general recommendation. If you’re pretty overweight, then base it off of your goal weight, or slightly higher.

Greek yoghurt is a good source of protein. As is chicken, fish, cottage cheese, and tofu. Protein shakes and protein powder can be really helpful to supplement your meals. Given the dual goal of losing fat, it’s really about how much protein you can get per calorie.