Responsive divs with text and images

I need to make a page with divs responsive. I-excel is a responsive theme but if you make your own divs then lost its functionality.

I use a main div and inside there are two others divs with text and images.

Here is my webpage that need the responsive design: http://logotherapeia-irakleio.gr/%CE%B5%CF%80%CE%B9%CE%BA%CE%BF%CE%B9%CE%BD%CF%89%CE%BD%CE%AF%CE%B1/

Thanks in advance!