Hi agata273,
Thanks for reaching out in Apple Support Communities. I understand that after installing the most recent iOS update to your device you're unable to open apps, compose messages and other issues using the device. I can see why you'd reach out about this behavior; I'd like to help. First, if you haven't already, a restart can help resolve behaviors similar to what you mentioned: Restart your iPhone
If you've already restarted or the issue continues, I'd suggest reinstalling iOS to your device. First, make sure you have a recent backup:
Next, use the steps titled "Put your device in recovery mode and set it up again" in the following resource. These steps will remove the iOS currently installed and replace it with a fresh copy, so be sure to closely follow step four and choose to "Update" in order to prevent data loss: If you can't back up your iOS or iPadOS device to a computer or restore it from a backup
Take some time to test your device after using these steps and let me know what you find.
Best Regards.