You got me blushing, ha ha, indeed I am not an English expert, just a regular visitor to this site, and I have learned some things English by sheer curiosity and some practice. However my skills are not that good, I just can get by, believe it or not!
Anyway, I decided at some juncture of life, that I could share my little I know of English; not much, but there are one or other student that is in more basic level than I do.
Now you would say "get back in touch" would depend on the context, if you say "I´ll get back in touch" you might mean "I´ll call you back/I´ll mail you later etc..." but as you may have understood, most of the time it means "entro em contato depois" or something like that.
(it is a way that mean both, to keep in touch or good bye - sometimes in a sarcastic way).http://idioms.thefreedictionary.com/Keep+in+touch
Indeed "matar as saudades" can be conveyed in a number of ways in English, here some of them (sometimes in an indirect way):
Obama's all smiles as he catches up
with long-lost family on official visit to Kenya.
I´ve been back to my city a few times to touch bases
with my family, my relatives, and have a big time.
And other ways...
take care, buddy!https://www.youtube.com/watch?v=D-vPR5ujU9Y