Can i use DX11 on C/C99? Its possible?

Yes, it can be done.

You don't get any of the COM interfaces automatically, which are free in C++. There are macros out there which do creation that sets up the virtual functions rather than automatic from the vtable, macros for onstruction and destruction.

You can use just about any language with COM, some are easier than others. Portability was a major design feature and is well built.