In Britain we say 'he slices the cheese' but perhaps I'm wrong in my translation. If he 'cuts the cheese' he doesn't necessarily cut through the cheese, he may just make a cut in the cheese - is this the correct translation? But why would he want to do this?
Re. farting, is this an Americanism?
"cut" was used long ago to mean farting. "cut the cheese" appeared in 1950s, implying the bad smell released by cutting through the rind.
As an American English speaker, "cut the X" implies cutting through the object, even hard ones like metal or wood. Some engravers and other specific cases may not mean "cut through". I've only used slice for bread and for swords. For cutting that doesn't go through "chip" or "dent" is more common.
Prepositions in Portuguese contract, so em + a becomes na. Here is a link with more details: http://en.wikibooks.org/wiki/Portuguese/Contents/Common_Prepositions_and_Contractions
On a lot of the translations, they want 'the' added to the portuguese sentence. They talked about in one of the lightbulb lessons from earlier. In fact, I think it was one about food, where they said that the 'the' is added to many things. Now I'm curious and will have to go back and find it or else I wont be able to go to sleep!
Update: I found it! It's in the Food2 lightbulb. It says: In english the words lunch and dinner are used in a different way compared to other nouns. They are often used without any article or determiner. In Portuguese though, they behave as any other countable noun, using the article to be definite: Lunch is ready= O almoco esta pronto They eat dinner= Eles comem o jantar If you dont use the article, the sentences would sound just like these bad English sentences: I have car. Boy is here. etc. That's it! I didn't, and still dont, understand all these grammar words, like definite article and determiner among many others I've come across here, but by reading their examples I get the basic gist of what they're saying.