I’m 15, have pubic and armpit hair, not deepened voice, precum when masturbate but no foreskin

I don't understand your question! 

No foreskin, worried about foreskin does this mean I haven't hit puberty yet?

Do you mean your circumsised and why you worried about not having one and reaching puberty?

No it hasn’t folded back

But most over things happens with puberty

So you have a foreskin then?
How do you mean folded back? Your foreskin won't retract unless you actually pull it back.
The signs you have pubic hair and armpit hairs shows you have started puberty, every guy/girl starts and goes through puberty at different stages an different ages and you still have plenty of time yet to develope more yet.

Basicly I have signs that I have hit puberty and a bit into but my foreskin is still a kids instead of adult and it dowse time look right with pubic hair and my penis is 6 inches erect

I still do not understand what you mean about your foreskin or how you think it should change, you have every sigh of puberty is well under way and as I said everyone goes through puberty at different stages at different times, you penis is over adult average already what is 5.1inches!

All males are born with their full foreskins as infants. Many infants are circumcised as infants right after being born. They cut the foreskin off the end of the penis which leaves the penis head exposed with a scar circling the penis below the penis glans or head ( the pink rounded top of your penis ). Other boys and men keep their foreskins which are different sizes that cover different amounts or cover all of their penis including covering the penis head or part of the head. Foreskins are different on each penis. Some are long and go past the end of the penis head. Some foreskins are medium or short and might leave the penis head uncovered or part covered. All of this is normal.
If you are circumcised, drs cut off the foreskin in different places and take off more or less foreskin. But all circumcised penises have a dark brown scar circling around the penis below the penis head where the foreskin was cut off. This cut scar can be right at the lower edge of the penis head or anywhere down the penis shaft below the head and up from the balls. Most scars are an inch or 2 below the penis head.
Circumcision is not needed. It is a needless surgery that cuts off the skin that is designed to protect the penis head and skin that feels great during sex and masturbation . People claim to do it for the looks of it and to make it easier to clean the penis head. Penises work great both ways. Both ways are common in different countries.