Water pump defective! And still 430 km to home…

Hello people ! I am with my wife and the 260er since a few days in Hamburg (live in Mönchengladbach, easy distance are about 430 km). Yesterday I noticed coolant loss and was therefore yesterday in a MB branch here in HH. Result: was actually clear: the water pump says goodbye and fast a repair is not possible, since we drive tomorrow (so Saturday) anyway back home. However, the master at MB said, with moderate driving mode and regularly the filling of the coolant tank should be the way to make it – but of course I’m worried. Therefore my question to you: do you see this as well ? Did any of you ever have similar problems ? Or do you have any other tricks in stock to master the track ? I am grateful for every tip ! Greetings from HH (is already a very interesting metropolis), tom260