"It is difficult to make windows."
Translation:Det er vanskelig å lage vinduer.
That's pretty much what we learned as a rule as kids in school. There are exceptions, but even norwegians make mistakes with those.
But it's actually quite complicated, and sometimes you have a choice. For instance "brev" (letter, as in sent by mail) can both be "brev" and "brever" in plural. And then there are single syllable words which require a -er plural ending, like "salt", which when you talk about different types of salt gets the plural form "salter". And sometimes the choice of using the distinct plural form can vary according to setting. For instance the word "poeng" can take the plural form "poenger", and is common when you talk about bullet points, arguments, and so on. While when you talk abou scoring points in sports, the prefered choice is to let "poeng" be both the singular and plural form.
Sabine is correct, with the addition that "gjøre" is also used with emotions, like "make me happy = gjøre meg glad". (and the auxiliary verb "to make" I believe is "å få")