Amazfit Watch faces

Hi there,
My T–Rex Pro watch does not have the screen locked, after I started a workout (for example walking). Before there was a red screen top with a lock sign. That is not anymore and I cannot switch it on. The locked screen is usefull when it is raining,
Does somebody know what to do to lock the training screen again?

By fortune, I found out how to lock the touchscreen during training to prevent rain drops activate unwanted functions.
1. Choose your training.
2. Wait eventually for GPS connection.
3. Push ’GO’.
4. Wait until the screen switches off.
5. Immediately push the touch screen.
A red field will appear in the upper part of te touchscreen with a lock on the right side.
The screen is locked now and water cannot start unwanted functions anymore.
Unlock the screen again by pushing one of the right buttons.