NeoNeper, there are just a few things to remind when working with C++ DLLs and Gamestudio. Most important is the fact that you have to use the _VAR() macro to turn numeric values into the var-representation, when passing to Gamestudio functions. The same goes for the other way round, please use always the _INT() and _FLOAT() macros to convert vars into numeric values.

Beside that, there are no special advices we can give you, since all other advices might be focused on C++ and for that, you can simply buy a book that handles that better than we can.