Failing at Design and Technology! Help!?

Hi! I have recently started doing GCSE Graphics and I'm finding it really hard. I had to choose a D.T. and I thought Graphics would be about drawings (cartoons, logos) which I really like to do (I'm really good at Manga). But, I struggle at making things and doing technical drawings. For example, we had to make a package out of paper nets. We used double-sided tape for sticking edges together. I was the only one not to finish, as I kept cutting into the paper using a craft knife then I couldn't even take the covering of the tape of the paper! I'm such a fail at D.T. but can someone give me some help or advice on how to pass with at a C or B.