Question for bodybuilding (muscle size)?

You shouldn't be able to lift the barbell more than 8-12 times (with perfect form of course)... it should be at your maximum weight, which is the best way to increase muscle mass (break down muscle and rebuild bigger)... then as the weeks go by, if you're eating enough of the right food (lean protein is important) and training enough (different muscle groups, 4-5 times a week), you'll be able to add weight and increase muscle mass... sometimes you can hit 'a wall' and find it hard to build any bigger, at which point you could maybe have a week or 2 of just cardio/ toning (lay new capillaries and increase potential)... change your exercises... or try a supplement (no steroids)... good luck to you!