Can't "vanavond" also mean "this evening"? We do often say "tonight" to refer to the evening, but we can also say "this evening."
Yes, it can also mean this evening. It can happen that a correct translation is missing in the system. In cases that you believe that correct answer is missing always use the report a problem function that is present with the sentence.
Yes, I usually do, but this time I managed to also make an actual mistake in the sentence.