Hi, fairly new TK user, started with lesson 1, mastered it. I can now move a piece of paper quite far, just by imagining the atoms/gases mixing into a thin long line, and it hits the object whenever I move my hand (and that seems to work out). But anyway, do you recommend I should open my third eye so I can move on to lesson 2, because whenever I try lesson 2, I'm not sure if I'm moving the object or my eyes are out of focus. So should I open my third eye?

That is a huge YES in my opinion. The third eye is most likely the basics of developing psychic abilities.

Yes, you should definitely open it!