It's so ambitious two split the game up in two styles and I think you managed to do that with great success! The look of the game is very unique and it fit this dark part of history perfectly. The only thing I disliked with the actual look of everything was the fact that it was a bit hard to know what was collidable and what what not. There was a fair few times I avoided obstacles because I didn't realise they were actually not - only to attempt to jump through them next time and realise it was a solid. The biggest issue I ran into here was during the top-down sections where I got stuck for quite some time running from the flames before realising I could actually run through what I'd thought was walls.
I managed to complete the fire-part, but I didn't get through the plague-part, where I never managed to get through the first top-down part. I think sadly that the controls during top-down took a lot of pleasure away from your otherwise nice and fun game. As stated earlier, holding "W" made the slippery feeling go away, but for some reason this only worked good enough to play through when escaping the fire, but I never got it working in plague. So sadly, that was very frustrating that the character suddenly acted like it was on ice and slid away into a skull. :< I tried a lot of times but eventually just had to give up. :<
I think overall that the plague-part felt more unpolished than the flame-part, in both ways I've already mentioned. The rats were also a bit hard to know the status of - like the white rats on the roof killed me a ton of times, and therefore I tried so hard to avoid them in the sewers(?) before I realised they were not dangerous there.
But I loved the look on both sides, it felt dark, saturated, old and "uncomfortable" (in a good way! I don't find the exact word I'm looking for here. xD ). And I loved how the story was written as you ran. I think a great addition to that would be to have the text follow the player for a slight distance somewhat, because it was a bit difficult to read when running and trying to time those jumps!
So gameplay-wise, a bit frustrating sadly, mostly in the top-down part, but in all other areas I think you did a great thing here. :D