Can I open Microsoft office 2011 docs with Libre Office ?

Since the Mac OS upgrade to Catalina 10.15 I cant open any Microsoft office 2011 docs. Can I open Microsoft office 2011 old docs with with Libre Office ?

Usually yes. Some particular sophisticated formatting or feature might be interpreted differently, but just give it a try.

Note that Catalina as some awkward “this is not an Apple approved program notion”, see this blog post for details and how to solve.