>>105717290
Malwarebytes is supposed to be good for removing certain malware that isn't picked up on by most antivirus programs, so it can be worth doing a scan with it every once in a while, but Defender seems well enough on its own, since Microsoft access to a lot more data and a better understanding of Windows than any other company. The potential issue with Defender is that because it's on every system, anyone making virus/malware is going to specifically design it to evade Defender, so it wouldn't hurt to have a backup antivirus installed just in case.

>>105717834
This would probably be too much effort and probably wouldn't work depending on how the video is encoding/compressed, but you could try just opening the video in an editor and seeing if the voice-over has its own track you can delete.
If it doesn't, but you are certain that the voice-over audio is in mono or all in the same stereo channels, you could try the old trick of copying the audio track, inverting the amplitude, then adding the two audio tracks together. The destructive interference should cancel out the voice track, but leave the rest of the stereo nature sounds alone. This technique used to get unofficial instrumental song tracks, since the main vocals are usually recorded in mono or in all stereo channels. It doesn't work if that isn't the case, though.
AI could probably just remove voice overs too.
Or you could just go outside and watch nature in real life.