BitDefender is a no go. Far too many issues. It works alright for some people but completely butchers other PCs.
You need three layers of defense. Antivirus, antimalware, and in-browser solution. While some top paid antivirus software does contain everything in one, it doesn't hurt to research.
Currently, Windows natively has its own anti-virus Windows Defender, and it works relatively well. The majority of the popular providers have free versions of their software to test out, and they also do the job. As for anti-virus, I recommend Comodo, Avast, Avira, Kaspersky or Norton. All of them proven formidable.
With anti-virus, you usually will need to run anti-malware software. Not every single anti-virus has the full package included. Any of the popular software solutions will be solid as well. My recommendations towards ADWCleaner, Malwarebytes, Hitman Pro.
For in browser solution, you could use an Adblocker to protect you from malicious ads, uBlock takes this one for me.
But when it comes to the internet, no software will protect you 100%. My tip would be to be aware of what you are browsing and downloading. Do not click suspicious links, avoid shady files. Additionally, be careful with emails, a lot of malware is spread through fake/malicious emails. That is the best way of being safe out there. Good luck!