posts arn’t cuztomized

I got wordpress up and running and it was all fine untill i tryed to write a 2nd post.
When i wrote my first post, it was fine. But when I wrote my second post, all my coding got messed up. As you can see:
https://www.kelly-element.net/x/
there is 2 posts there, one comes up fine, but the other post all the coding has messed up.
I don’t have a single.php file (and i feel i should have) and i customized my blog in the main index template file because it worked on the first file. Please comebody help me because Im completly stumped