You must work with more cells and split differently.  Also adapt the widget in the height.

Example:

why do I have such a large space under the widgets??

I really can't find out how to avoid a very large empty space under the widgets like Google news or Gradient buttons, this situation disordenates the whole layout.

How can I get control over the size the widget takes?

Thanks for helping

There is a simple fix for this, when you insert a widget box  you have to make the height 0 then you wont see that space. check the picture i have attached. good luck.