Adjust the shape automatically to text?

Is there that sort of option?

I don’t want to keep readjusting my “boxes” with text. I would want some of the boxes automatically be adjusted.

Yes. The options are on the Text Inspector.

If I may, I’d like to take the opportunity to plug our free User Manual, available in the iBook Store. It’s very comprehensive. (190 pages!) More information about the different sizing behaviors is available on page 130 of the (current version of the) manual.