form of stretching is always
required to have the foreskin retract. We have to conclude that in most
cases, this happens with a normal degree of "playing" with the penis in childhood, as well as "nocturnal erections" - the frequent and prolonged erections which happen every night during (certain phases of) sleep.
Even just the automatic action of gripping the penis whilst peeing - when it is usually, at least in young fellows, erect - will over time
tend to promote retraction, and "playing" frequently develops into more definite masturbation.
The point is if you are past
this period of growth, you have apparently missed this opportunity for whatever reason; a combination
of the particular growth pattern of your
penis and for whatever reason whether lack of curiosity or some event which might have caused you to be averse to touching your penis in the usual manner. We will therefore conclude that this will not
correct itself without formal stretching and you need to work on the exercises.
That said, nothing about your present situation prevents you from undertaking any sexual activity nor affects your fertility whatsoever, even if you never "corrected" it. As such, even without knowing any more than the meagre detail you have given us, I suggest to you that it does not matter
how long it takes, that there is no hurry.
clearly the case though, that the more diligence - regularity and frequency, and with the right technique
- that you give it, the quicker you will see results.