How do I reset language using key commands if I am logged out? My dog stepped on the keyboard and reset the language to Greek and I have no idea how to log back in

You can just type in the password by looking at the keyboard and not the screen -- but give it a try -- it might work. Then after you login go to System Preferences and select keyboard icon and then Input Sources tab and make sure the "Show input menu in menu bar" checkbox is checked (this is the first checkbox in the list of three) and then click on the flag icon in the menu bar and set the keyboard to US.

If that does not work, try booting up in single-user mode -- hold the command+s key down during power up.

Then follow the instructions on mounting the root file system as writable at the bottom of the screen. Something like

/sbin/fsck -fy
/sbin/mount -uw /

That first command will take a little while - so wait for the # prompt before typing the second command. After the second command wait a second and then type return key again - you should now be at the "localhost:/ root#" prompt.

Then go to /Users/yourusername/Library/Preferences and move the file com.apple.HIToolbox.plist using these commands:

cd /Users/yourusename/Library/Preferences
mv com.apple.HIToolbox.plist ../../Desktop
cd /
exit

That should do it. Wait for the GUI to come up and then login as normal.

If you had defined other keyboards that you really want you need to add them again as before.

Good luck...

Hmmmm, interesting problem, maybe in Recovery?

https://www.macworld.com/article/3330638/macos-recovery-foreign-language-fix.html

Launch Terminal, which is in the fifth menu from the left, labeled Utilities in English. The apps have icons next to them, and Terminal is a little rectangle with a prompt in it. After Terminal launches, type sudo languagesetup and press Return. You can then select the language to use.