Enable Qwerty Keyboard
Galaxy Watch 4 still comes with a default T9 style keyboard. It is an old-school type keyboard that used to be supported by old keypad devices.
However, devices with T9 style keyboard has become obsolete. We don’t know, why Samsung is using the old T9 style keypads to date. I personally hate this style as it creates difficulty in typing.
Thankfully, Google play support lets you get rid of the old-school keypad by replacing it with a qwerty keypad called Gboard. You can finally install the Gboard application from the play store.
To change your default keyboard type, Go to Settings > General > Input > Keyboard List > Tap on Default keyboard and choose Gboard.