I’ve probably shared this on T-nation before, but I’ll share it here as an encouragement for you, @Ismail999 , since it sounds like you want to try out for something military.
You stated your weight and height but I know neither your age or build, so that weight/height could mean you’re fat or muscular, or both, but definitely not thin and scrawny like I was when I started doing pullups.
I was a non-athletic teenager with a lot of awful things in my life, and I decided I’d join the military. Pullups weren’t part of the US Navy’s entrance requirements, but it generally seemed like a capability I’d need, so I resolved to develop it.
I couldn’t do one.
I drove big nails into a pair of trees, threw a steel pipe across the nails and duct-taped the pipe onto them so it wouldn’t fall off.
Then I drove nails down just above where my feet would be, and used them as footholds to boost myself into a pullup using my legs.
You can do this with a doorway pullup bar and a stool, box, or chair, obviously.
Do this as many times a day as you can, with as little assistance from your feet as you can, until you can do a pullup. (You already can.)
Then maybe it’s 1 pullup and 2 or 3 assisted pullups.
Then maybe it’s 2 pullups and 3-5 assisted. and so on and on without end.
Once you can do a few, develop a habit of just coming back, again and again, and doing more.
I also really like EMOM training for this. You might start doing one pullup every 2 minutes, for 10 rounds. AFter a few of these sessions you could get to one every minute for 10 rounds.
After a few rounds of this, doing 10 pullups starts to seem feasible - and from there, your own motivation and other goals will take over.
That’s basically how I did it. I got to the point of 20 pullups while still a young man (no idea exactly when, but let’s say age 20-21?)
Once you’re good at this, you find yourself (in a military environment anyway) constantly hanging off of overhead features. Monkeying around on pipes and ceilings, or having pullup contests with the other guys. It is a positive-feedback cycle and you just keep getting better.
Today, I’m 37 years old, 190lbs and 6ft tall, and I can go crank out 20 pullups right now, cold, or hang from a bar for 60 seconds, or do a weighted pullup with probably 60-70lbs.
Can I squat as much as a 14-year-old girl? No. No, I cannot. But god dang it I can do pullups! 