@kmar123 I have the same probelm! Also, I'm quite experienced with dumbell exercises and several types of bodyweight exercises like lots of push-up variations so I supposed I could do a pull-up or even chin-up but not even close. I could get a chin-up once, but I was underweight so NOT in a good shape at all. Didn't have even nearly as musch muscles as today.
I figured there are some movements you need to train as they are to be able to do them. Cardio, HIIT and dumbell/ push workouts do improve my endurance and strength together with a routine that make sense - remeber progressive overload and not too much at once or in a short period - but they won't teach me pull-ups without working on them and as well. Get even enough sleep, food and recovery. Remember to eat well even on rest days.
When I try to run outside, I get several probelms
-out of breath and so much slower in comparison to others
-when the air is cool, my nose starts to run so bad I can't breath through my nose. Not nice trying to run without breathing
-but I can't stand hot weather so if it's like +30°C outside I can't go jogging because I'd die. I can play tennis even then, though, because that's something I'm better at
-there's wind, hills and varying surfaces that makes it harder for unaccustomed feet. I do better on treadmill because it's easier inside
If I wanted to run a marathon I'd try to start practicing slowly but surely, little by little and understanding it's a new skill that I haven't practiced yet. It probably takes a while to get accustomed to training outside and getting into the flow but I've understood that when you go running often you can get nice results pretty fast even if your runs weren't really long or fast straight from the beginning. Train with your own pace, not with others, with consistency you WILL get better