Welcome to D-A-L
Not sure what you mean by
"I set my computer up to speak to me in German".
If you mean that you have the German version of XP installed then you would need to purchase an English version. They are two different products.
If you meant otherwise pardon my confusion and please elaborate on what you have done.
Your screen resolution can be adjusted via
start Control Panel | Display | Settings
If XP was pre-installed you should still have either an OEM Recovery CD or there should be a Recovery partition on your Hard Drive.
What is the make and model of the computer?