I'd kill to look like that but I assume drugs are involved.
Also I'm 35 and waaaaay out of shape (like walking up stairs or fairly short distance gives me sore muscles the next day lol and im over 350 lbs of almost all fat) so idk if like the timeline age wise would be bad.
Whatever the amount of stairs you need to walk up so that your muscles are sore the next day, do that, take a breather, do it again, take a breather, do a third one, take the next day off. Do that three days a week, for two weeks, and see if it's getting easier.
That's not a complete fitness plan, but it should do fine for the first two weeks.
If you want more homework, start eating salads and vegetables. This doesn't have to replace any existing meals, but try to eat your vegetables before meals, and stop eating if you're not hungry. The goal with that is to get used to eating healthy food, so you have options later when you need to start reducing calories.