OK, so I've known a number of Scottish people and I've been there a couple of times and generally had no issue understanding them.

However, when working in London years ago, I had to talk to someone based in Scotland on the phone and her accent was just insane.

Honestly it was exactly like this post, she'd say something, I'd say sorry what and this repeated 3 times then....we both burst out laughing. The most insane Scottish accent ever!