Chosen Solution

Two of my arrow keys (left and down) do not work anymore, or only if I press with huge force. Can one fix that?

Yes, by replacing the keyboard. 3 options;

  1. Replace the whole palmrest (more expensive, but easy) MacBook Air 13" Mid 2011 Upper Case Replacement
  2. Replace just the keyboard (keyboard costs 10$, but more difficult) https://www.youtube.com/watch?v=2PyhbiwU…
  3. Pay someone to replace it (cost varies depending on area and repair shop)