If your Raspberry Pi 400 seems to be entering the wrong keys compared to the ones you're pressing, it's usually due to the configuration setting within Raspberry Pi OS.
Go to a terminal window and type 'sudo raspi-config'. Then head to 'Localisation options', then 'Keyboard layout'. What you should need (for UK users) is the Generic 101-key PC English (UK) variant, however if that doesn't work please try the other options listed.
If you're outside of the UK, test the different options for your specific region/language to check which works best for you.