Are there foods which not only prevent but help fighting cancer?
The short answer is, no.  There really isn't any good evidence that a person can eat enough of any chemical to have a clinically detectable effect on cancer.

Note that any study that shows an effect on cancer cells in a petri dish doesn't count as demonstrating that it would do anything in a person with cancer.  It might be that the chemical would not work the same in the body, or would not work the same on real cancer cells growing in a person (not cells cultivated to grow in a petri dish for 30 years).  And even if they did kill cancers like in a petri dish, that doesn't mean that you can actually eat enough of the chemical to get a high enough concentration to have that effect.

That link is pretty much click-bait, and nothing more.