Take care of yourselves
Türkçe'de take care of yourselves nasıl denir?
kendiniz iyi bakiniz
kendinize iyi bakın
you may say "kendinize iyi bakınız" but this is ridiciliously polite, and usually you don't say "take care of yourselves " to someone you talk extremely politely to.
so what should I use if I want to say this to a bunch of close friends without being too formal !
It is "Kendinize iyi bakın" as she said above and for singular it is "kendine iyi bak" as said below.
"Kendinize iyi bakınız" stands for formal you(both singular and plural) yet you would not hear it from anybody among the speakers and the reason is explained above.
For formal singular you just use "Kendinize iyi bakın" again if you ever need to.
Thank you so much, I got it.
How do I say keep in touch if it's a popular saying in Turkey.
I would not call it popular in Turkey. We usually just say Görüşürüz<see you>, but in my opinion, "let's keep in touch" can roughly be translated as "Haberleşelim". I would personally use that phrase to a person I'm neither formal nor informal but as I said it's not common.