swissdoc, I will say this as politely as possible while giving you the best advice possible. You have no business starting any kind of A A S right now. Aside from the fact that you have very little "practical" (not medical) knowledge (which is why you are here in the first place), you do not have sufficient time to invest in training at the gym and following a proper diet. A A S are NOT a substitute for proper training and diet, it is a compliment to them.
Also, I'm not sure if you're completely recovered yet from your major surgeries, but keep in mind that the theory is if you're engaging in A A S, you are pushing your body beyond your typical daily limits. That being said, you run the risk of increased injury if you're not careful. Given your surgeries, I would be even more concerned.
Give yourself time to learn more from those more experienced, make sure you are fully recovered, find yourself enough time to train at least 4-5 days per week, and follow an appropriate diet. Then you will be ready for A A S.