Translation:It is a good opportunity not to have lunch at work.
Seeing as this sentence refuses to go away, maybe I can offer another explaination as to why this is so baffling in English.
I can't think of any case where one would ever refer to not doing something as an "opportunity" in the English language. "Opportunity" typically refers to a chance to do something advantageous. The word refers to circumstances rather than actions. Here opportunity seems to refer to the verb обедать, whereas in the English translation it should refer to the time period allocated for lunch. A better translation for what the Russian sentence is trying to say (I think) would be "Lunch time is a good opportunity to get something done". But I think that would be a confusing translation for this lesson, so I still think this should just be removed.
I don't think that is the meaning of the Russian sentence. "This is a good opportunity to have lunch outside of work" or something like that, seems like the way one would phrase such a thing in English. In Russian it seems that "having a good opportunity not to do something" (if that something is somehow "bad") is ok, but in English it generally sounds very strange, so the sentence would be paraphrased so that you have the opportunity to do something else.
Maybe just "This is a good opportunity to avoid having lunch at work", using the positive verb avoid to negate.
This sentence in Russian might be commonly used and easily understood by all. However, the person who created this example needs to understand that a literal translation to English does not work here. If this IS a widely used sentence in Russian, I have no idea what it means in English. If it is not widely used in Russian, it has no place in a Russian language course. What is the author trying to say?