So I'm about to start building a steel KV-2 from scratch for a school project. But I need such things that cant be made from scratch, such as tracks, optics and so on. Where do I get that in the correct sizes?

I'm thinking about making the tank 1/10 or close to that.

If you want, I could start a project thread when I've begun the building?

One track link ought to be easy in that scale due to the size. I'd use Evergreen styrene. Then you can cast up resin copies. If it has to be metal, look into to building a backyard aluminum foundry. I've been doing some research on this myself, and it looks interesting. Are you going to be doing any lather work?
If you go 1/9 scale you night find a few weapons already made . I know there''s a lot more in 1/6, but I'm not sure how many WWII items are available since it's not my thing. It might be worth looking into before you settle on a scale.
Good luck with it.

Well, I'm gonna be doing all this at school because we have a welding workshop, and I have access to normal steel, rust free steel and aluminium in thicknesses between 1mm and 6mm.

I have access to all materials for free. Though bearings and things I can't make from scratch, I will have to buy myself.

I also saw that there's many things in the 1/16 scale, so I think I'm gonna have to stick with that.

I just discovered that my local Ace Hardware store sells bearings of all sizes. (this just months after turning my own on lathe) I'm sure Norway has similar stores. No sense in reinventing the wheel.

Well of course we do. We arent as uncivilized any more ; ) I'm also able to do lathe work if needed.