Position of the blog post on my website

Hello,

I am new to WordPress, even to CSS, HTML and PHP. I am trying to learn and setting up my website – https://www.contentonweb.in

I am playing around the home page and completely modifying the Twenty Thirteen theme. I have messed up a lot, but trying to learn. I have Made some changes in index.php and sidebar.php.

My problem is, you will see that the content (entry-header) is positioned a lot below in the container of the class – .site-content.

I have done everything to fix it, but have failed. it happened due to some changes I made in the index.php file. Please help me out. Tell me how to get the posts back to their position.

Thanks in advance