Hi all! Glad you enjoyed the review, as I had a lot of fun with the game! I'll answer your questions as I can here!
I didn't have any performance issues at all, actually! I played on iPhone X on Ultra resolution and never noticed any slowdown or problems. Originally I started out on the lowest graphical setting and worked my way up while I checked for these kinds of problems, but happy to report I didn't have any. It's possible, of course, that this is due to the fact that I'm on iPhone X, but I don't have any bugs like that to report, especially with the massive amount of buildings and people onscreen, which really impressed me.
The Expert level was challenging in that it was necessary for me to go in and micromanage the city as I mentioned in the review, so I felt there was a lot more of that required from me, and that's why I kept it from being a 5/5 review.
The only problem I actually had in terms of crashing or bugs happened just once, and it wasn't a crash. It was a light pink panel that would appear on my screen after a tornado or thunderstorm. It appeared over my map one time and wouldn't go away until I closed out of the game entirely and went back in. It didn't affect my experience or anything, just peculiar. I've played two cities simultaneously since starting the game up, and haven't ran into any problems with losing progress or crashing, so again this could be due to the phone I'm using, but nothing but stability over here!
Also, no, I haven't found a way to pause the game, but it seems to me that suspending it and going out of the game pauses at the very least the money you make and the cool down timers for events/disasters.