Form with side by side content area and content flowed.

Hi I have issue with the logic below,

i have a master page with 3 content area, 1 at the top header and other 2 side by side below the header. My requirement is like Header content may increase, in such case, the excess left content area should fill in right content area.

Filling the content works prefectly, but the problem is the right side content gets overlapped with the header text, this is not the case with left side content.

Could anyone help me on this.

Also please suggest me if any alternate way to do this.

Below is the image

Thanks in advance.