Hi there! I understand that the Booking.com app is crashing on your iPhone running iOS 15.8.3 after an update. Let’s work through this together to find a solution.

Here are some steps you can follow to troubleshoot the issue:

1. Restart Your Device: This is often the simplest and most effective solution. Press and hold the power button until you see the slider, then slide to power off. Once it’s off, wait a few moments, then turn it back on.

2. Check for Updates: Sometimes, developers release quick fixes for app issues. Go to the App Store, tap on your profile picture at the top right, scroll down to see if there are any available updates for the Booking.com app. If there are, go ahead and update the app.

3. Force Quit the App: Double-click the home button (or swipe up from the bottom if you don’t have a home button) to see your open apps. Swipe up on the Booking.com app to close it completely. Then, reopen the app to see if it still crashes.

4. Reinstall the App: If the above steps don’t work, try deleting the app and reinstalling it. To do this, press and hold the Booking.com app icon until a menu appears; select “Remove App”, then confirm by tapping “Delete App.” After it’s deleted, go to the App Store to reinstall it.

5. Check Storage Space: Low storage can sometimes cause apps to misbehave. Go to Settings > General > iPhone Storage, and check if you have enough free space. If space is tight, you might need to delete some unused apps or files.

If none of these solutions seem to work, it might be worth checking online for specific issues related to the app and iOS 15.8.3. You can find discussions and solutions that might be relevant, such as this thread on Apple Support Community which talks about app crashes on this version of iOS.

Let me know if you need further assistance or if any of these steps helped! Are you satisfied with the solution I provided?