I'm using galaxy s6 for more than 3 years now and have no issue while it. But from last couple of months I'm facing same issue and that is ads pop up itself regardless what I'm doing on my phone. For example watching videos on YouTube, making phone call, texting or WhatsApp etc it appears on the top of the what I'm doing. I factory reset 3 times I think but after few same issue appears. I uninstall most of the apps now I'm using what's app, keep, messenger, Ali express, Dropbox, outlook and default apps. Samsung Internet browser is default browser with ad block. These are the pictures of the ads, theses are examples every time top is different but appearance is same.
Regards.
Regards.