Hello K1200R,
Since Messages doesn't respond as expected, let's force close and then relaunch the app using the steps below:
1. From the Home Screen, swipe up from the bottom of the screen and pause in the middle of the screen.
2. Swipe right or left to find the app that you want to close.
3. Swipe up on the app's preview to close the app.
You can also find those steps in this resource: Close an app on your iPhone or iPod touch - Apple Support
Should that behavior still persist afterwards, you'll want to reach out to Apple Support: Contact - Official Apple Support They'd be in the best position to look into this further.
Take care.