Hi Elderotter, we just pushed out an update less than half an hour ago that fixes some issues that was making the game get slower as the city grows. Please update to 0.1.13413 and hopefully that will solve your issue.
Please note that there was a bug in the game that let too many citizens walk around at once in the city - and that was causing a big performance issue. If you load a save that has a lot of citizens walking around, you may not immediately see a big performance increase - but performance should increase as you continue to play the game!