I'm not at my own computer now, so I can't make any wireframe for you. But to your questions about columns and rows:
The usual number of columns in a grid is 12, and I think you should stick to that. Seeing the drawing you made, you could in theory reduce the number to 4, but I would advise against it, because then you are locked into a very rigid kind of grid.
So, it looks like you need 4 rows. The 3rd one down should be split into 3 - 6 - 3 cells' columns, and in the middle one you could drop a subgrid with 3 rows.
The 2 top rows (of the main grid) both has a navigation. You can either split the right part of those rows into single cells to hold a nav button, or you can insert a navigation from a different programme. Also the logo and the image to the right will be in columns covering the number of cells needed for those two items.
When narrowing the screen width, at some point you will see that everything starts looking very small and squashed. Click the plus sign (top left) to insert a break point a little before it becomes unreadable. Then do some editing to the 3rd row (maybe the other rows need it as well, depending on your contents). If the image background in the two 3 cell columns only serve as decoration, you could take them away and make the 6 cell column cover 12 cells. If, however, the image backgrouns have to be visible, You can also make them 12 cells wide and float them so that the left one goes above the middle section and the right one below.
Have a go at it, it's not rocket science, after all.