Why does my Galaxy S7 autocorrect apostraphes to quotation marks

[AC Question]

I'm recently an apple convert so if this is obvious please excuse my lack of knowledge. Basically whenever I type email's or Facebook messages on my new S7, while attempting to use appropriate grammar, the phone auto corrects to something useless, for example, he's becomes he", isn't becomes isn", they're becomes they"e. When I try to type :s it comes out as ::. I've checked my language and input settings and it says I have no auto correct on. Attempting to back space the auto correct and retype the rest of the word again gives even worse results, ttey'e being the auto corrected result of they're. I've virus checked the phone and it said secure.

Any help would be greatly appreciated.