Revise design for website I made for walking fitness group

Hello, I'm instructing a group of young adults on how to walk on a treadmill while doing things (such as watching TV). I'm building a website where I can teach them the importance of walking and we'll have little competitions to log in their walking each week! The site will have lots of text. So I organized it into four sections. The first (main) section is attached below as a PNG file. The other ones are attached further down. I already have a basic layout-I just think it needs some revising. There are a few things I'm not sure about, and I'm looking to see if someone can improve the design a little. My goal is to make it easy for others to navigate. Here is what I have for the first section (see below) If you're interested read more below and set a bid! Thanks!![first level][1]