Can I write a regular expression or regular grammar for this language?
This language is context-free but not regular. It is isomorphic to the problem of matching open and closed parentheses: (n)n which is a well-known non-regular language. To prove this yourself, you would use the pumping lemma for regular languages.

Every regular grammar describes a regular language.
This language is not regular.
Therefore, there cannot be a regular grammar that describes it.