Hi Jad_Gh,
Welcome to Apple Support Communities. We understand that you're having an issue with entering your password for an in-app purchase. We'd like to help.
You mentioned that you are unable to rotate the display to see if that helps. Is that because you have rotation lock on or just that it won't change for you in this specific game? While it may be a limitation within that game, checking if that lock is on is a good first step:
Rotate the screen on an iPhone without a Home button
1. Swipe down from the top-right corner of your screen to open Control Center.
2. Tap the Portrait Orientation Lock button
to make sure that it's off.
3. Turn your iPhone sideways.
If the screen still doesn't rotate, try a different app — like Safari or Messages — which are known to work in landscape mode.
Learn how to rotate the screen on your iPad.

If it's still not working, these steps should resolve it:
1. If an app on your iPhone or iPad stops responding, closes unexpectedly, or won’t open
If an app on your iPhone or iPad doesn't work as expected, try this.
2. Close and reopen the app
Force the app to close. Then open the app to see if it works as expected.
3. Restart your device
Restart your iPhone or restart your iPad. Then open the app to see if it works as expected.
4. Check for updates
To see if updates are available for the app, open the App Store, tap your profile icon, then scroll down to see if updates are available. If updates aren't available for the app, update the software on your iPhone or iPad.
5. Delete the app, then redownload it
Delete the app. When you do this, you might lose data that was stored in the app. Then redownload the app. Then check to see if the problem with the app is fixed.
Hope that helps.
Cheers!