So, I have made a tutorial using this method:
*Record with Kazam and save as .mp4 which is default for Kazam.
*At the same moment record sound with my phone, which unforutunately is very old. I don’t have microphone, so I use my phone. It is Java phone.
*Send the .amr file to computer and convert to .wav.
Now I can’t find a working way to mix this sountrack with video. If anyone wants to help me out using Windows, PM me, because it is hard to figure out correct software in Linux and I don’t know much about video editing…