Just a thought

[Dominantly]

I don't think I saw it mentioned, soooo one thing you could try in situations like this is to eliminate the interior lighting. I was doing the same thing at my familys house in front of the tree and rather then deal with the different lighting temps in the room, I killed them all. IF you set the cameras exposure up for grabbing a nice background, including exposing the tree with it's lights nicely, then hit the family with off camera (or on camera) lighting, you can get some good results.

 

[IgsEMT]

Kaspar I didn't say you were attacking but since you mentioned

I've been in the game since Christmas(well I had my camera before that but never really understood anything)

I've been in photography starting 1999 learning on Bronica using 150mm, 100mm, 80mm, 65mm, 50mm lenses with Quantum and lumedyne flash units (portable) and white lighting, later dynalites were used for portraits and room lights. For 35mm, photographer I was assisting/learning from was using Nikon f100. In 2002-2003 I began shooting using the two bodies. In 2004-2005 I started using D70s (photographer's) and D50 (my own). In 2008 I began working with few more studios and using theirs Nikon D200, D300, Canon 5dm2, 5d, 20d, 40d, 1dm2 (or m3, don't remember), as well as both brands' flash gear and later my own D90.
Now that we done bragging about our backgrounds, mine isn't that impressive. There are people on this forum who have experience 5-6 times GREATER then mine and have taught me a lot both in camera gear operation and processing. So let's not talk about backgrounds here

There's no question that primes are smaller, lighter, produce sharper images, and at times cheaper then zooms, however, every equipment has a proper use.
Plastic, cheaper lenses aren't built great BUT with proper processing (either in camera or on PC) can produce decent enough results. However, if you don't know how to set up portrait above, sorry Giorgio , then your image will come look like it did no matter what lens you'll be using. It isn't the gear at fault, it is lack of knowledge --> one of the reasons why many people come here and post their work and learn to further improve their skills.