If the picture that I put of your site is what you mean, leave it alone. If it's not broken don't fix it, it's fine the way it is. There's not a site in the world or what we do that we wouldn't change even as soon as we do it. I've done these type of things and it's ended up in a mess when there's been little wrong. If you want to play do it offline or on test site.

It's more than just that. The twitter box is covering part of your menu and the text below the images, the two birds at the top will cover the heading/logo.

Responsive web design is a completely new approach, but if you are interested in learning, google it. Also, google something called 'mobile first'. It's a principle about creating a site for a small screen first before a larger one. It's easier to do it that way insterad of starting with a wide screen site and then squash it to fit into something smaller.