Avira is pre-installed on my laptop.
Should I extend that or get someone else?
You can do what you want, there's no 100% protection!
Windows Defender is enough.
Use the in-house Defender! Everything else makes no sense.
I have avast for normal everyday things that is enough if you want internet banking you should take something more stable
In / under Windows 10, the native Defender is really sufficient and the third-party whipping oil is not absolutely necessary. Especially since the clutter can also become a problem. I would install a maximum of Malwarebytes and thus temporarily (against) scan your system.
If that is not enough for you and you absolutely want to spend money, I would recommend BitDefender. I also set it up for my father. Mainly to keep an eye on the devices from home. You really can't complain about the price-performance ratio and the protection actually runs silently in the background.
I myself only use the Defender of Windows and I save other hocus-pocus in terms of antivirus programs. I only added GlassWire to my firewall. It is simply "just" a monitoring tool with which you can keep a better overview of what, where and how a network connection is or would like to be established. Quite practical, actually.
Especially since Win10 is the longest virus in the world.
