Protein deficiency will kill you; as will protein excess. Same is true of any nutrient. As you increase the intake of a nutrient, its utility first increases, then reaches a plateau, and eventually starts to decrease. Once it’s in the negative, it has potential to kill you.
The ideal amount of protein to consume per day is somewhere between 200 calories to 600 calories (~50 to ~150 gms).
Interestingly, proteins help in both losing weight and gaining muscle mass. Proteins have a satiating effect; so people consuming low amounts of proteins feel more hungry and eat more food, thus consuming more calories. This effect plateaus around 15% protein intake.
Proteins also signal to the body that there’s enough food in it and so it can focus on muscle growth. This is why higher protein intake helps grow muscles. Note, however, that muscle growth is mostly supported by a high calorie intake. As long as you are near the higher end of the 200-600 calorie spectrum, increasing protein intake will not help grow muscles. But increasing calorie intake helps, no matter what the composition of the calories.