When your goal is to build muscle in the gym ditch the isolation exercises like biceps curls & triceps extensions or at least use those exercises only as a workout finisher. Instead focus on compound exercises which are exercises involving multiple joints. They will alter your hormonal response to the workout in a way that relatively quickly leads to a better body composition aka more overall muscle & less fat!
My Favorit exercises are pull-ups, lunges, push-ups.
If you prefer weighted exercises you would be well off with benchpress, deadlifts, squats, military press, rowing etc.
Happy workout! 💪😊