I just posted a reply to foreskin retraction to another tread, But you are in your twenties now which makes it a lot harder for; I actually had Friend that had a similar problem at around this age and he ended up having to be circumcised.and you may to.
But you can try these excercises which may help you enough.
1: Get into a warm bath if you can,or even put some warm water in a Basin and immerse your Genitals in it Heating them softens the skin
2: Before you retract you Foreskin, Grab it at the front with your Thumb and Finger and pull away from your body stretching more.Let go of it; and then repeat the process,do this a number of times.10 or more.
3:Now put your thumb and finger somewhere around the middle of your penis and begin to push the skn back to the base. ( the reason for this is that you are lessing the full amount of skin that will end up behind the Glans) Depending on how much overhang you have you will notice that the glans appears.
You should now have gathered some skin close to the base of your penis,Hold it there and if your glans is still not fully exposed, use your other hand and do the same with that.
You now should be clear of the glans,( if you still have some adhesion to it,apply a little pressure on it over a period of time, Meaning over many days/nights)
4:If you have succeeded and the Skin passed the Ridge(corona)you have done it and this little routine exercise; regularly will have you good in no time
5: When you want to pull the foreskin back ( and at this stage you are likely to have an erection,and maybe in a little pain and discomfort)Don't panic yet:Reverse the process
Push as much as the skin as you can to the base of your Penis, this will take away pressure from the Glans.Holds as much of it there as you can, and use your other hand to ease the skin back up along the shaft towards the head,and over it. You may have to give the edge of the glans a small squeez as you are doing this it should work.
You have missed so much in life only discovering now that your foreskin is suppose to retract
