Is there any thing to increass my stamina and metabolism and is there any way to last longer before I cum so we can screw longer
Well you have two options, you can...
1. Give all of your attention to getting her off and then once she does you can get yours. Like give her oral sex.
2. Go ahead and get off then you'll have about 20 minutes of down time before you can go again. So use this time to pleasure her and get her off. Take your time. Then once she does then you're up and ready to go again.
practice holding in your pee ( that's longterm help )
masterbate with the other hand if you always use the same one (longterm as well)
when you masterbate, stop right before you cum, go soft, and start up again
pull out until your soft and start up again.