seem and Once

[kahhong]

hi there, how to use seem and once in the sentences?? \\\\thank

[Tdol]

Once- can mean one time and when:
I'll make dinner once I get home. (when)
I have been to Vienna once. (one time)

Seem- have an appearance of something
He seem to be very stressed- that's the impression he gives, but it might not be the case