"They are not going to open that box."
Translation:Níl siad chun an bosca sin a oscailt.
Yes, that’s what I’m saying. (There are also other ways of expressing the “intending to” meaning in Irish.) Note that a sentence like “They are not going to that place” could use chun for “to”, but it couldn’t use chun for “going to” with its “heading for” meaning; that meaning of “going” would be translated by e.g. ag dul instead.
Go raibh maith agat! I am sure it will be a long time before I figure out the words order on these sentences (yes, I have read the explanations but don't understand them so it will take a while before it is understandable to my way of thinking) but maybe I can remember when to use "chun" now anyway, now that it was explained this way.