Huawei P9 Lite - Manual (Page 188)

Accessibility Features
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Select an item: Touch an item with one finger to select it (it will not open). The phone
will read out the content of the selected item.
Open an item: Double touch any part of the screen using one finger to confirm your
selection from the previous step.
For example, if you want to open Settings, two steps are required: Touch the Settings
icon once using one finger, and then touch twice on any part of the screen.