Would "Darllena gyda dy athro di" and "Darllena gyda eich athro chi" be used? I'm still a little confused on how to use possessives properly.
"Darllena gyda dy athro di" would be fine. However "Darllena gyda eich athro chi" is incorrect because if you're using the plural or formal "chi", it would be "Darllenwch gyda eich athro." (With the final "chi" being optional.)