It seems to be nicely responsive, but you need to insert some images to see how it works then because they behave differently. It’s one thing to make a dummy layout, but it must be tested with actual content, always content first, then create a layout to accommodate it.
You are using fixed heights which are generally best avoided. content should dictate height, hence ‘content first’. You are forced to add a fixed height because there is no content.
I also notice you are using in-line style attributes 
.
Please do yourself a favour and replace those with classes and put all the styling in the css.