loading slow and not saving posts

Hi,

My website is loading slowly. We’ve optimized all the images, but both the front end and the back end are loading painfully slow. In addition, I write posts and save them, then go to preview them and the content isn’t there. When I look at the revisions it says that the most current revision is showing but it isn’t. I am not a developer, so I am completely at a loss for what to do.