Samsung Galaxy Note 4 — Downloaded Touchwiz by accident

I am new to this forum, actually its the only forum I was ever on. I have been trying to research my issue for over an hour now and I need an answer that is put into the simplest terms. A lot of the questions and answers are to techy for me to understand, I am also coming from having an iphone for the 6 years to having a Samsung Galaxy Note 4.

If someone could answer my question and dumb it down for me I would really appreciate it.
I downloaded Touchwiz (I was just trying to download a new calendar) and my whole phone changed. I spent the weekend adding widgets to the different pages and putting my apps into specific folders, but once I downloaded Touchwiz everything disappeared. I want to get my phone back to the way it was when I first purchased it. I have had this phone for a few months so I don't want to do anything that would delete all of my pictures, videos or apps.

All I want is to get rid of this touchwiz and get the stock setting or whatever the original setup was called back the way I had it set up before I lost it.

I know some people are going to think I am stupid, and yes I will agree with them. I am very stupid when it comes to Android devices. If someone is feeling nice enough to explain this to me in the simplest terms (like you are talking to a 2nd grader) I would really appreciate it.

Thank you!!