New structure for subforum

[epsilon80]

I would like a subforum like this:

then in two columns and the column without LAST MESSAGE.
Can you tell me how to do? More or less I understand that I must act on a variable, but as this is only one, inserting it appears obvious, in a single row with 6 cells. And this is a problem because some of my subforum comosti are more than 15 sub-sections, and then ccreerebbe a single row with 15 cells: S
but I would like to divide them into two main columns, you know help me?