The pop-up warning is only a precaution by Google, saying that the keyboard may collect data from your input, but the app is well regarded.
You can select multiple languages by tapping on more than one.
The 4-row layout is best for when the device is in portrait mode, and the 5-row layout is more efficient when used in landscape orientation.
You can use the arrow keys when on the 5-row layout to move the text cursor, as well as the Esc key when using PC emulators on your Android device.
