I don't see the issue...both "I have good grades in French" and "I have got good grades in French" are correct English sentences meaning more or less the same thing, and "I have good grades in French" is shown here as the correct translation...could there have been a typo or something that caused you to get this question wrong?

"I have got" is more commonly used in British English.

By the way, this sentence is not totally correct in proper French where "des" becomes "de" in front of an adjective.