So I'm playing a Drakewarden Ranger who gets a drake companion with it's own stat block. In the drake's languages, it speaks draconic. Other creatures (such as guard drakes) specifically say they understand but don't speak draconic, so can the drake comanion speak draconic or just understand it? It is a drake, but on the other hand it behaves differently to other drakes, having wings in later levels among other things, so I need to know.

Per the Monster Manual on reading stat blocks:

The languages that a monster can speak are listed in alphabetical order. Sometimes a monster can understand a language but can’t speak it, and this is noted in its entry. A “ — ” indicates that a creature neither speaks nor understands any language.