I follow the havo subjects mathematics B, biology,...

I follow the havo subjects mathematics B, biology, Dutch and geography at nha. The lessons are well structured, but often they are far too long: 28 pages or more in mathematics, for example.
I have two teachers who are very nice and give me useful tips and additions. Unfortunately, the other two teachers put less effort into it and never give me feedback, while their site says: "Our teachers guide you during your studies! They assess the exercises you make while studying the full exam material. ''. Unfortunately, I hardly get any guidance from the two teachers I talked about, they simply check my answers.
When I contacted customer service about this, I was not treated kindly and no understanding was shown.