Basically, the DA42 is a light twin certified to and operating under a different set of regulations to transport category aircraft. You don’t need to worry about V1, screen heights or second segment climb performance.
A wet paved runway makes little difference to take off distance unless there is significant standing water, it’s the braking performance if you need to stop that is important. Wet grass would probably be the equivalent of a contaminated runway for a large aircraft.
Paved runways are generally longer than grass ones, and other factors such as weight and density altitude are usually more prominent.