Is it possible to debug a mixed assembly?

Here I have a .net application, which is a third-party assembly and I DO NOT have its PDB file.

When I try to explore it, well,  it's never obfuscated, but a mixed assembly which includes Native methods start with '__Cxx'. What I can see are only declarations,  not procedures.

Is it possible to debug a mixed assembly? And what should I do?

Thanks.