after apple update my Youtube and Instagram stop responding

To fix YouTube and Instagram on your MacBook Air after the latest macOS update, you need to determine if you are using them via a web browser (like Safari or Google Chrome) or as independent apps. Since Instagram does not have an official desktop Mac app and YouTube is primarily used via the web, a recent macOS update most likely corrupted your browser cache or extension settings. 

Step 1: Force Quit and Reopen Your Browser

If your browser has frozen or stopped responding, force it to close: 

1. Press Option + Command + Esc on your keyboard to open the Force Quit Applications window.
2. Select your browser (e.g., Safari or Chrome) from the list.
3. Click Force Quit.
4. Hold down the Shift key on your keyboard and click your browser icon to reopen it. (Holding Shift prevents the browser from trying to reopen the corrupted windows that crashed it.) 

Accumulated cache files from before the Apple update often conflict with the new system software

• For Safari: Click Safari in the top menu bar > Settings > Privacy > Manage Website Data. Search for youtube and instagram, then click Remove All.
• For Chrome: Click the three dots (top right) > Clear Browsing Data. Select Cached images and filesand click Clear data.

Thank you WheelieNick but it didn't work I don't know what to do !! Apple you should fix it !!!