How to keeps adds away on my Samsung s5?

I have a samsung s5 and I keep getting adds on it. No matter what in doing they pop up. They are games adds. I will be reading a book, texting someone playing minecraft or even at the home page and my phone will turn grey and an add pops up. I don't know how to get rid of it. I even downloaded an app to get rid of the adds but it dosnt work. I asked my mom (who works for samsung) and she didn't even know how to help or even know why it was happening. I got adds a while ago and then they just stopped for a long time and now it came back. Please help I really hate this problem and appreciate your help. Please answer back imediatley.