How does "příliš" mean "too hard" instead of "too much"?
"too much" is also an accepted translation but it is more common in English to use "too hard" here
'zbytek' means 'rest, remainder'. I expected 'zbytečný' to mean 'remaining' but it means 'useless'. Is there a relationship?
Remaining can be zbytný and as an archaism even zbytečný.
Yes, there is a relationship, I think the etymology should be quite clear, something not needed, something that remained unused...
Makes sense. Thank you.