Dell XPS 13 (9343): Video & audio problems

Hi everyone

I bought a Dell XPS13 9343 two years ago. I've never had any significant problems. The only thing that bugged me was that sometimes videos behaved a bit difficult - they would move in slow-mo and without sound if i clicked fast forward or backward (way) too often.

Now I have serious problems with audio and video. It started a few days ago. Whenever I pause a video and do something else (even just for a few seconds), i can't restart the video i.e. press play again. The video then does the slow-mo and no-sound thing. I can only solve this by reloading the video, which is really annoying. 

The other problem I have is the sound. Whenever a sound comes on for the first time, it's incredibly loud, even though it's not supposed to be. This happens with or without headphones, sound muted or not. An example is when I start a video - bam, really loud. If I click the volume I already set, it goes down to that volume. 

I've already downloaded new drivers and the newest Windows 10 update is installed as well. The problems happen on web-based videos and .mp4-files saved on hard drive or flash drives. Flash player is integrated and activated in Edge.

Has anybody experienced the same problems? Any solutions, please? I'm kind of desperate, because I can't work like this.

Thank you so much.