It's appropriate to say 'buenas tardes' any time after 12:00 noon. It's O.K. to fudge a few minutes before noon. You can continue to say it right up to near dusk, or the dinner hour. The dinner hour usually is the watershed for beginning to say 'buenas noches.' If you meet someone at 6:30 p.m. in the summertime, and they say 'buenas noches' while the sun's still shining, it means they've already had dinner, and this is 'night' for them.
goodnight is "bonne nuit" in France.
Well, I'm a girl, and I would say that some of the best ways to say goodnight to girl depends whether you're saying it to her or texting/messanging her. If messenging her, then don't say it too late, and if saying it to her, then a simple goodnight is all it takes.
Buenas Noches
Buenas noches, guapo.
Que tengas una buena noche.
You can say "lafi" to say goodnight in Mandinka.
In Berber, you can say "tanemirt" to say goodnight.
"Goodnight".
goodnight
goodnight!
In Fulani, you can say "Jaama wolof" to say goodnight.
In Pangasinan, you can say "napagtolak" to mean goodnight.
Either could be used depending on context. For example, "I said goodnight to Mary" or "I said goodnight and Mary said goodnight, too." The first sentence implies that I directed my words toward Mary and not toward someone else. The second sentence means that both Mary and I said goodnight, without specifying to whom we addressed our words. You would generally say goodnight to someone. You would rarely use the word "too" after goodnight. If you did, it would mean "also."
shab bekheyr
In Polish, you say "dobranoc" to wish someone goodnight.
In British English, you can say "goodnight" or "night" as a shorter version.
In Sondhi, you can say "ດີ່ນກັນ" (dien kan) to say goodnight.