I was just as confused about where to start with this series. There's a bunch of titles floating around, and honestly, it's a bit of a mess because the novel was serialized under different names and translations are all over the place. The core story is 'Medical Return'. You should begin with the main novel under that title.
After that, things branch. There's a side story or continuation often called 'Life of a Successful Surgeon' or something very similar—I've seen it listed as an official sequel. That's the next logical step. Then, if you're really into the world, there are some spin-off stories focusing on other characters, but those are harder to find in a complete, orderly fashion. My advice? Follow the main character's timeline: start with the medical school and residency drama in the core novel, then move to his established career in the follow-up. The fan-translated epubs I found grouped it that way, and it felt right.
Honestly, you might hit some dead ends looking for perfectly clean translations of every side piece. I gave up on a few and just stuck to the two main arcs, which tell a complete enough story.