I am 28 years old. It is embarrassing and very demoralizing that I cant jump-rope. I see all the boxers in my gym do that. I also cannot swim, or ride a bicycle. I also cannot run more than a mile continuously, after which I start getting cramps on my right rib area.

As you can tell I don't fit the description of a fighter from any angle. I used to play basketball a lot, I could play 3 full court games one after another. Then I tore my ACL, followed by my meniscus. There was no sports surgeon in my country and I could not afford one abroad. So I sat on my couch and grew into a potato over the next two years. Now I can barely run a mile. I have been doing MT for a bit more than a year now. And I love it and I want to compete in the rings some time down the line. I study the sport, I watch videos and I like learning about it.

Sparring someone on my skill level, I perform great in the first round, but then I am just a walking heavy bag.

So what is it that I need to do before all else? Learn to skip? focus on running? Take private swimming lessons?

I have seen this and most answers suggest skipping and running.