I'd really like it if you tell me what can I do to improve my jumping position , my instructor says it's good , but because i'lll start jumping higher than what I usually do , I guess I kinda have to improve it .
Its not from the picture. Your crotch is over the front of the saddle. And your leg is sliding back as a result from it (more so in the first picture). You should be hovering over the center of the saddle. Counting strides helps you get a distance, but you need to use your horses motion to push you out of the saddle and fold your hips. If you are coming to jump and you aren't getting enough impulsion don't jump for your horse, instead drive him forward with your legs and sit and wait for the jump to come to you.
I also think your stirrup lengths looks good...not too short at all.
I agree. Your stirrups don't look too short at all. And when ErikaLynn said you are jumping too far ahead she meant in front of the motion. You are in front of the saddle. Counting strides doesn't make you not get ahead.
Remember to keep your heels down and toes in. Use your horses motion and legs to get you out of the saddle, not your stirrups.
I Like your flat back and that your are looking ahead! :)