I’m wondering if, when you say the C is too high or too low, are you trying to match it with your singing voice?

Or it is something about the guitar itself that does not sound in sync with me on the videos?

if it’s your voice, then that is perfectly normal - scales start low and go high and the keep going forever (theoretically,!) in both directions.

there is likely only a sliver on that spectrum and span that we can match up with our voices, and then it gets too high for us, or too low for us, to sing along with.

Humans.

-Lisa