Your people are very old, some even think the being of the beginning of time itself.  You've been told stories of the old ways, shown how they work, and sometimes you yourself tell these stories.  So you would be familiar with all thing from the time before.

All languages that are over 2,000 years old you can read and speak.

Specifically: Celestial, Primordial, Infernal, Draconic, Sylvan, Deep Speech, Common, and Urspeech

Also lesser known languages:

Yeti
Winter Wolf
Worg
Sphinx
Otyugh
Giant Owl
Giant Elk
Giant Eagle
Druidic
Blink Dog
Aarakocra