Meatball and potato soup

I am looking for a polish soup with pototoes and meatballs. The meatballs had an unusual take, maybe majoram. My mother called it 'Fass' or 'Kfass'. Do not know the polish spelling. It had a sweet/sour taste.

Not sure. But Poles usually eat potatoes and meatballs as a second dish (not a soup). But let a female gives her opinion .

Meatballs are good. The more balls, the better they are.
That sounds like "żurek" which is also called "kwas" because it's made of a soured wheat base. You can make it with meatballs or kiełbasa.
And majoran is a basic seasoning for this.