@Ch40zz: Sorry but I don't understand it clearly enough, yet.
Now you can access all the functions from the SDK.
To initialize the Steam API you have to put this code into your DLL exported init function:
What exatly do you mean by 'DLL exported init function'?
And to access functions of the steamworks api, do I only have to create the function's prototypes in lite-c or do I have to wrap the functions in the c++ dll-project?
Sorry but this is all new stuff to me.