Our team is presently looking into lag reports with high priority. We regret any inconvenience this may have caused.
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. Should you choose to use a task killer, we suggest excluding SwiftKey from being killed in such a manner. Otherwise, SwiftKey may temporarily disappear without your knowledge.
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.