My mb 2010 glk 350 does not start after fueling it takes several times and finally starts. No check light on.

check fuel filter if you have run it out of gas several time than the fuel pump will pump the dirt that is in the bottom of the tank into the fuel filter

If you have a habit of topping it off and squeezing every drop you can in to tank, bad idea. Stop at first click. The EVAP canister gets saturated with liquid gas and will cause a hard start. If you don't do that, and do stop at first click, the problem may still be in the EVAP if it starts normally otherwise and only happens after filling up.

What do I do after I changed fuel pump, to get it to start

Change the purge valve!