Unfortunately, there aren’t really any direct things we can do to solve this issue – but we are keeping lag issues in mind!
We’re constantly trying to address lag issues in SwiftKey with some devices, but our prediction technology does need the phone to do a fair amount of work! In the short term, making sure only one language is selected at a time, and using an app such as “Advanced task killer” all might help to improve speed.
It may also benefit to free up RAM resources on your device.
If you have questions on how to do so, please let us know.