- Do a right click on the loudspeaker symbol on the right bottom of the screen

- select the entry for playback devices (the second from the top)

- select the device you are using for audio output

- select properties

- disable all extensions

- click restore default on the bottom (Standard wiederherstellen in German)

- do the same for advanced settings (farmost right tab, erweitert in German)

Maybe you have changed a setting here when you tried to fix your audio output. 

One more remark: Windows 10 runs just fine, unless you mess up or have upgraded from a flawed system. In this case a fresh install will help to fix things. Just upgrading a system that has been running for years maximizes potential problems.