your 20 mins arms/shoulder is not right dude.. you should be working according to minutes.. do sets and reps.. more sets less reps = mass.. less set more reps= strength

well i've only been working out for about 2 months, but this is what i've been doing and i've stuck to it.

monday: back and legs. i do 4 sets of pullups, 4 sets of bent rows, 4 sets of trows, 4 sets of squats, 3 sets of leg presses, 4 sets of deadlifts, 4 sets of back extensions, and sometimes 3 sets of back flys, 4 sets of calf raises, 3 sets of leg extensions, (not always in that order though) then i play basketball for 2 hours.

weds: chest and shoulders. i do 5 sets of flat bench, 4 sets of incline bench, 3 sets of decline bench, then 4 sets of incline flys superset with dumbell presses, then 3 sets of regular flys (by this point my chest is destroyed haha). then i do 3 sets of front shoulder presses, 3 sets of reverse shoulder preses, 4 sets of arnold extentions, 3 sets of regular shoulder extensions, 4 sets of front shrugs, and 3 sets of reverse shrugs, then i play basketball for 2 hours or so. (i do my ab routine on either day depending on how much time i have)

friday: i dont have time to go to the gym any other days so after work i do bi's tri's and forearms. i do 4 sets of standing curls, 4 sets of preacher curls, 4 sets of incline dumbell curls and 4 sets of standing hammer curls. then 4 sets of skull crusher tri raises, 4 sets of lying down tri raises with the curl bar, 4 sets of dumbell tri raises (sometimes i alternate bi and tri excersises to save time). then finally i just do dumbell things for forearms, i dont know what those are called until my forearms feel like their gonna die.