Not able to add media and super slow

For a while now my “Add New Post” page has been extremely laggy. Even when editing existing posts, it’s super laggy. When I go to do something such as change font, change font size, bold, underline, etc. it will freeze for about 10-15 seconds before I can begin to type or click anything again. Additionally, today while writing an article I was not able to use the “Add Media” button. So therefore, I could not add any photos to the article. I could click on it, but it would not do anything. When right-clicking on it, it would not give me the option to “open link in new tab” or “window”. “Add Form” and “Add contact form” still work fine though.

The page I need help with: [log in to see the link]