So if I'm at Olive Garden in Sweden and they offer me cheese on my lasagna I can be like "Ja tack!" or would they be like "yes thanks what ??? whatever I'll just give him some cheese so he doesn't complain"
No, they would not be confused. The literal translation is "Yes thanks!", but it is the Swedish equivalent of "Yes please!" So "Ja tack" does not mean "yes please", but you would use it in place of that.