Okay, you were right about the tween is confusing the table cell positions because of other table element's anchors.
I found a basic solution: I switched the table cell alignment from "top left" to "top".
This works smooth, but only if every table element's transform.X = 0. Otherwise 'weird things happen'.
Problem is, that every tween motion adds a number to all gameobject's transform.X, and after 3-4 tweens the whole table blows up. I could write a function that always set transform.X=0, but it seems a really clumsy way to solve this.
Another question: I'm not experienced in nGUI, I came to Unity from web dev, and in html is soooo much easier to make anything like this UI. Why is a responsive scrollview with some things in it so awfully hard to make? Is it too much for nGUI, or am I doing it in a very wrong way? (I worked weeks on this **** scrollview - still doesn't work properly, and in html it would take 20-30 minutes to make alltogether - I'm very frustrated

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Thanks, - and sorry for my lang, I'm not native english speaker