- Disable secureboot and legacy boot
 - Enable EFI (UEFI) boot
 - Boot
 -  
loadkeys cz-qwertz -  
ping archlinux.orgtest internet connection - If no internet:
-  connet ethernet cable
- If ethernet cable connected and still no internet
-  
modprobe -r tg3 
 -  
 
 - If ethernet cable connected and still no internet
 
 -  connet ethernet cable
 -  
modprobe broadcom 
Essentially just copy the existing video and audio stream as is into a new container, no funny business!
The easiest way to "convert" MKV to MP4, is to copy the existing video and audio streams and place them into a new container. This avoids any encoding task and hence no quality will be lost, it is also a fairly quick process and requires very little CPU power. The main factor is disk read/write speed.
With ffmpeg this can be achieved with -c copy. Older examples may use -vcodec copy -acodec copy which does the same thing.
These examples assume ffmpeg is in your PATH. If not just substitute with the full path to your ffmpeg binary.