The quickest (and simplest) way to turn into a fit beastly athlete is to do sprint intervals. Find a little field near your house, and just sprint as fast as you can for about 60 yards, walk slowly back to where you started, and do it again, repeat about 10 times, and then go home and eat a lot, and do it again the next day.
It's actually the ultimate exercise, works every muscle in your body, is much easier on the joints than jogging, and gives you god-like stamina too (you'll understand why after your first day- it is surprisingly tough, but that's good), and dramatically will improve your agility and explosiveness, you'll walk around with a spring in your step and just feel great.
Just look at the physiques of sprinters compared to marathon runners, or anyone, they have perfectly optimal bodies and are absolute machines. Mind you they do a lot of other exercises/weights, but start with sprinting, that will get your juices flowing and then you might be motivated to do other things. Boxing is good too, hitting a bag. Doing pushups is underrated too. When I was at my absolute peak I would jog 5 kms, then do 10 sprints and after each sprint I'd do 20 pushups where I bounced up and clapped my hands, I'd do this every second day, and on the other days I'd do weights or boxing. Was a great feeling, I just walked around like a boss and then inevitably found a girlfriend that turned into a wife and then I let myself go, lol. But this is actually motivating me to start again, because it was so much more than just looking good to attract a female, the coolest thing about it was being a beast, being capable, having endless stamina and being fast and strong and agile.