Honestly i would find another teacher. Preferably a guy who can demo in person for you to hear what he sounds like. Even if he can do it, doesn't always mean he can teach. But it's still better than someone who can't do it at all

Females talk in head voice most of the time, so their main challenge is strengthening their chest voice. Guys have the reverse problem since men typically speak in chest voice, so the head voice is lacking.

Mixed voice can only be developed when you have a strong head voice. Primarily the OO and EE vowel, descending scales note-by-note from A4. Keep working on those and your head voice will grow. If your teacher doesn't teach using vowels at all, find another one