We are always working on optimizations. That said, if you want to speed up your game now, you can try a few things.
Was it always slow?
First, think about if the game has been slow since you started playing. The first levels in the game are the best performing, so if it was even slow then, there is likely nothing that can be done on your end to fix it.
Make sure it's not a lag bug!
If your game has gotten very slow, and it is slow even on the World Map, then it could be a bug with lag. If you are experiencing this, then please send us a message.
Try Selling Bubbles ("Loot Orbs")
Do you have a ton of Loot Orbs sitting around your Camp? These have a lot of particle effects and can slow down your performance if you have a lot. You can try selling them -- you will get the full price of the stuff inside.
Try Zooming In
The further zoomed out you are, the more the game has to draw to the screen, which slows it down. You can try zooming in a bit to whatever level is tolerable.
Check your Battery Life Options
In the Options menu from the World Map, check what your setting is in Battery Life. If you toggled it to "Battery Saver", this can make performance a bit choppier.