I have had to interact with regional managers at MB before, and in my experience, their job is to dismiss problems rather than to resolve them. Regional managers are handlers.
It is possible that all MB C class manual transmissions behave as yours. Only way to tell is to drive a some and find out for yourself. If car manufacturer’s cars all behave the same way, they do tend to say that the behavior is normal. It does not make it right. The bad news is that, if this is the case, there is nothing that anyone can or will do about it.
If after trying a few cars, you find the transmission is still not satisfactory, absolutely do not accept the other car. Either get one with an automatic transmission or get yer money back. I don’t know have first hand experience, but seriously doubt that MB will retro fit an automatic transmission into a car built with a manual transmission.
Best of luck!!! Keep up posted!