Turn off repeated key presses
By default, when you hold down a key on your keyboard, the letter or symbol will be repeated until you release the key. If you have difficulty picking your finger back up quickly enough, you can disable this feature, or change how long it takes before key presses start repeating.
Click the icon at the very right of the menu bar and select System Settings.
In the Hardware section, click Keyboard.
Turn off Key presses repeat when key is held down to disable repeated keys entirely.
Alternatively, adjust the Delay slider to control how long you have to hold a key down to begin repeating it, and adjust the Speed slider to control how quickly key presses repeat.