I have this string like thing on my penis and when i pull the foreskin back it pulls the head down. how do i fix this???

Is it broken?: As the saying goes, "If it ain't broken, don't fix it." Also, we have to decide what the "string" thing is. Maybe it's something brand new. That means a trip to one's doctor to check it out. Maybe it's been there since birth. That's more reassuring but still usually needs an exam, but a video consultation with a good camera may suffice. Maybe it's the frenulum (one can look that up to see).