
Fast metabolism is a rhetoric from the government that isn’t a thing 99% of the time. You most likely fall within the normal spread but gaining weight and lean mass is as simple as tracking your calories figuring out your BMR and eating .75 to 1 Gram of protein per pound of ideal body weight
As you’re working out right now focus less on form and what you eat. Your priority’s should be this in order 1 hit your daily calorie intake, 2 go to the gym, 3 recover sleep and recovery is by far the most important part so get a minimum of 8 hours and stay very hydrated. Also remember it takes times you probably won’t see any results for at least 3 months