Fiber makes your body able to use the protein you consume. Form is most important. Do not get caught up sacrificing the correct form trying to go faster. It is always better to perform exercises slowly and focus on proper technique. This gives far better results than just trying to pump out reps as fast as possible. Going slow can also force you to incorporate more muscles into the move and make you work harder by eliminating momentum. If you want to increase muscle mass, you need to eat more food as well.