Your keyboard is made up with columns and rows like a spreadsheet. In your case the row line has failed.
Do you have one key which is worse than the others? That key is shorting across its column line with the row line so the other keys when they are pressed are not registering there state correctly.
At this point You’ll need to replace the keyboard. This is a big job you may want to fid someone who’s replaced Mac keyboards before or try to find an uppercase [https://www.powerbookmedic.com/MacBook-Air-11-Top-Case-with-Keyboard-Mid-2011-p-126069-o-7256.html|11” MacBook Air 11" Top Case with Keyboard (Mid 2011)] Here’s the guide to put it in [guide|10031]