Question

¿Qué quiere decir “Buenas noches”? what does this mean? how do you respond to it

Answer 1

Hello:
Why not use the verb *significar*, that is "to mean".

Example:
*Buenas tardes* significa "good afternoon".
(*Buenas tardes* means "good afternoon".)

Now with your sentence...
*Buenas noches*...

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Note: Here is some vocab you may need:
"morning" = *manana* [first *n* should have a tilde on it]
"afternoon" = *tarde*
"night" = *noche*

Hoping you now know how to answer your question...!
Blessings