I know you can convert every context-free grammar into Greibach normal form grammar.
But can I convert every deterministic context-free grammar into deterministic Greibach normal form grammar?
If by deterministic GNF you mean as a deterministic grammar that is also GNF then yes, here is the paper. Normal forms of deterministic grammars
EDIT Here is a paper outlining the technique to do the conversion Strict deterministic grammars and Greibach normal form