Mac Pro says safari browser not supported
I have Mac Pro, which unknowingly I put Bitdefender on, including VPN. I recently took it in to Apple Store and employee said to not have VPN. and took it off. The banner "this browser, (Safari) is not supported"kept coming on when I was on my email page. It disappeared after employee took it off and unchecked things. When I got home its right back on there again.. I am tech not smart, but I do keep everything updated. Everything I have is Apple. Any ideas? Also Safari seems to not be able to open pages like it was before either. Thank you in advance for any help!
Vicky
iMac 24″, macOS 15.1