Do you have an unfinished Daily Challenge or Quest task that's a Group-send job ??
Usually that's Youngsters or the older quest send Springfielders jobs that cause my games to slow right down.
If it's a Daily Challenge they now use up to 60 for the Springfielders group, not too bad, but bigger towns can have heaps of Youngsters.
Those can be dismissed to swap for another task, If it can't right now or it's a Quest job just get it done.
If you've got some of the "rides" from the Itchy and Scratchy Land event, like the Injury 500 racetrack, then turning the animations for those off or even storing them might help speed things up.
If none of that applies check your device Recent Apps screen and shut everything else down before tapping should help speed it up by freeing up memory. Worth seeing if you can clear Storage too for the cache files it uses while it's running.
The only other surefire answer is to upgrade to a better device, sorry.