chenjie108 wrote:"I don't understand"
"I can only speak a little elvish"
"What does ... mean?"
ú-chenion = I don't understand
Pelin pedo pîn edhellen = I can speak a little Elven or
Pedin pîn od i lam edhellen = I speak a little of the language of the Elves
I can't really translate 'Never mind' as it is, it'd have to be more 'Forget it', which doesn't exist in Sindarin either. I'll have a look at whether I can change a Quenyan verb into Sindarin for that.
Your last sentence is deceptively complicated...
Some options are -
Man te? = What is it?
Man sa? = What is that?
Man i theled od...? = What is the purpose of?
Istol man '.....'? = Do you know what '.....' (is)?
(The word 'is' is always implied, there's no word for it in Sindarin).