German phrase
Danke, aber ~ ist zu viel.
Meaning
Thanks, but ___ is more than I can eat
When to use it
It politely declines food. Use it when the amount is too large in casual settings.
Example dialogue
Möchtest du noch etwas essen?
Would you like to eat anything else?
Danke, aber die Portion ist zu viel.
Thanks, but the portion is more than I can eat.