2001 golf gti 1.8t 5speed stalls after 15 minutes and won't start back up what could do this

Is the check engine light on?

no

it did come on in the beginning

You need to scan it. Sometimes a crank position sensor failure can shut it down as you describe.

the code that was in there was the o2 sensor and that was changed also.

does anyone have an answer

What caused you to replace the fuel pump and relay? Expecting us to "have an answer", we need as much information as possible. Are there any codes currently in the fault memory?

2001 golf gti 1.8t 5speed stalls after 15 minutes and won't start back up what could do this. changed the fuel pump fuel pump relay vacuum hoses-- the code that was in there was the o2 sensor and that was changed also.

no they were cleared

I'm not understanding why the fuel pump was replaced. That's why I'm asking about codes. Does the fuel pump operate as you crank the engine? Did it before this issue? Coolant temperature sensor could be giving wrong info to ecu causing improper fuel mixture. Once it's stalled and you attempt to restart it, is the fuel pump operating then? Does it have spark at that point?

Because trying every thing to stalling. going through everything On;y code 02 sensor and that was changed to.