My Workout

I have been training for a bout 2yrs…I am 5’9’’ and about 170lbs.
For my workout i do 2 muscles a day (Chest/Back…Legs/Shoulders…Arms)
I do as follows 4exercises Per Muscle 3 sets for each exercises except the 1st exercises,each set is (12,8,6 reps increasing the weight) Example…Chest(Flat Bench 12/8/6/4…Incline (12/8/6)…Flys(12/8/6)…Decline(12/8/6) Back (Pull Downs 12/8/6/4) Rows (12/8/6) T Bars (128/6) ect…Now i was curious if anyone had advice on my workout yes my weights are going up but im having trouble gaining weight. If you know of a SICK diet or a better workout please tell me also…How many grams of protein does the body absorb at once i have been told (40/50/42) Please tell me so i know how much to take instead of taking more and having it be wasted