>what has alot of protein?
Meat, Chicken, Eggs, other stuff I can't think of right now but you can also get Whey Protein for on avg. 50 bucks. Ideally you want to intake 50g of protein post workout to feed muscle recovery. Don't go over that because the body can't process more than that at one time, so ideally spread it out throughout the day. Overall you want to 120g or more, not exactly on the level of your bodyweight. I also recommend buying Creatine Monohydrate and taking 10g along with your post-workout protein as creatine is a substance used to build muscle the body doesn't get very often.
>how do you do this?
Simple, on each day I work a different part of the body. A Push day is chest, shoulders, and triceps, a Pull day is upper and lower back, biceps and fore arms, and Legs is legs, calves and core work. Each part of the body is given 24 hours to rest before being worked again, and 1 day to completely rest to prepare for the next week. I also make sure to get 6-8 hours of sleep in order for my body to fully recover. When starting out you need to power through the initial phase and get your body used to the punishment your dealing it. 2 days out of the week might simply not be enough stimulus for your body to get used to it thus necessitating a much longer recovery period. Personally when I do 4 sets, the first set is a warmup that is half my max, and the next to sets I try to hit at least 8-10, and then on the last one I add 5lbs and go until failure. Then on the next day in the cycle that weight on the last set becomes what I do on the 2nd set, then the next day the first set as I add 5lbs more on my final one. This ensures progressive overload without biting off more than I can chew with my form failing.
>last set is the one you struggle the most
You need to keep adding more weight otherwise you will plateau hard and won't be able to get bigger. You don't have to hit 12 every time, just within the 8-12 range. Bro Split is where you hit one area of the body per day, and Progressive Overload is adding more weight over time to make yourself stronger,