3 sets of 5 reps, is this set/rep scheme good for building mass too?(if I eat properly and enough) Or is it mainly for strength gains?
It is good for building mass, especially if you're new to training. It is not ideal.
If you eat right then you will gain mass. I dont think set/reps makes much of a difference for the average lifter wanting to put on mass.
zig zag your goals. Gain strength with sets of 3-5 reps/set to failure
Then use that new strength to gain serious mass with 8-10 reps/set to failure.
When you see gains slowing, zig back to strength, with new strength you should be able to put up a heavier weight for 8-10/to failure, which stimulates more growth.
I used to do a couple weeks mass, a couple for strength. I am slowly coming to the mind that, for myself anyways, I should focus on one or the other for 4-6 weeks.\
Theres no straight path to straight beastin it, its a zig zag at best. If your always trying to train for both strength and mass, most likely you will achieve substandard results.