Sir, my foreskin comes behind at the time of erection but gets stuck behind the glan and the glan becomes red and sir my glan is a bigger than the others, sir i am doing streching exercise too will there be no problem or can there be more problems?

This is one of the medical reasons where some form of foreskin release/modified circumcision is worth considering. Even a limited cut in the foreskin can limit chances of an acute problem where the foreskin creates a tourniquet effect leading to amputation of the glans.

Your foreskin is tight. You can make it stretch gradually by gently pulling it all the way back then forward using a little cortisone ointment/cream as lubricant several times a day. Always keep the foreskin covering your glans. Gradually the tightness will go away. The other alternative is a circumcision. I hope you do well.