A lot of couple got trouble importing video files to Cubase or Nuendo. But here is my free tool of choice for Windows:
https://www.xmedia-recode.de/
You can try this other app:
https://www.shutterencoder.com/en/
For apple AND windows you can use MPEG Streamclip_
http://www.squared5.com/
www.sounth.de