How to handle a slow function from a dll

Hey guys, I am doing one bug of my application which is one function we called from a dll takes too much time to return so that the application will be stucked for a while(about 10-15 seconds). Is there a way to solve this situation without touch the function inside the dll? Thanks.

No, you need to change the code in the DLL to be either a coroutine or work with threads (which may not be possible depending on what the code does, since Unity functions are generally not thread-safe).