Can a Kipor KDE 7500STA power a water pump?

Your generator is specked at 6kva so it can supply 25 amps at 240v a standard 3 HP motor at 240 draws 12.2 amp but even if your name plate is 15 amps it should be fine, the pump will pull the generator down a bit at start but once it is up to speed there is room to run other things. I know my well pump I just installed this year and it only draws ~60% of new name plate value once up to speed and that only takes a second or 2. I have monitored it with the system pressure just under 80psi when it shuts down and that’s when I measures the highest current again at ~60% of the fla value. Added: I did not see your peak but did see the rating of 5.7 - 6.3k , even at the lower number you should be fine. Being a diesel here in the us costs way more but they usually last longer, it also has some nice features that less expensive generators don’t have.