Re: when texting my Galaxy 6S autocorrects.
Settings>System>Language and Input>Select keyboard you are using by default. Under there you should see all of the auto correcting options. Such as auto capitalize, auto space, auto punctuate, and auto replace which is what you will want to turn off.
If you are only wanting to have auto correct off while you are texting and not at other times, there isn't a way that I'm aware of to do that.