volume/luminosity volume lost

Hello there, Clement.

It seems you're having a few issues with the built-in keyboard and trackpad on your MacBook Air. The following Knowledge Base article offers some great steps to try for troubleshooting keyboard and trackpad issues:

If your Apple wireless mouse, keyboard, or trackpad aren‘t working as expected

Your mouse or trackpad doesn't track as expected

Apple Wireless Mouse, Magic Mouse, and Magic Mouse 2 can be used on most smooth surfaces; however, if tracking issues occur, try these options:

• Choose System Preferences from the Apple menu, then choose Mouse. Set the Tracking slider to adjust how fast the pointer moves as you move the mouse.
• Try using a different surface to see if the tracking improves.
• Turn the mouse over and inspect the sensor window. Use compressed air to gently clean the sensor window if dust or debris is present.
• If multiple Bluetooth wireless devices are in use nearby, try turning them off one at a time to see if the issue improves. Bandwidth intensive devices could affect tracking.

Learn more about what to do if your trackpad isn't tracking correctly.

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Your keyboard has one or more keys that don't respond

Use the Keyboard Viewer to test whether the keyboard keys are responding correctly when they are pressed.

1. Choose System Preferences from the Apple menu, then select Language & Text.
2. Select Input Sources.
3. Select the Keyboard & Character Viewer checkbox.
4. Enable the input source for the keyboard layout you're testing by selecting the checkbox next to it.
5. Make sure that "Show Input menu in menu bar" is enabled.
6. Choose Show Keyboard Viewer from the Input menu in the menu bar.
7. The Keyboard Viewer showing the keyboard layout appears on your display.
8. Type the key on the keyboard that doesn’t respond and see if the corresponding key highlights on the Keyboard Viewer. If it does, that key is functioning correctly.

Notes:

• If the mouse keys feature in the Universal Access System Preferences pane is enabled, many of the keyboard keys may not respond as expected.
• If issues persist, try starting up your Mac in single-user mode to see whether a software issue is causing the issue.

Thanks for being a part of Apple Support Communities.

Kind Regards.

Hello again, clement.

Thanks for the follow up on your issue. Due to the nature of the issue you described you may find more information by using another one of Apple's support resources - https://getsupport.apple.com/GetproductgroupList.action.

Regards.