When I publish a blog post, all the styles I used in writing it are overwritten.

I'm trying to post a new blog post, and whilst editing, the styles all seem to be there correctly, but when I upload, the styles appear to be overwritten, especially for the heading tags. I'm not that great at HTML, so I have attached my HTML editing box too if I made a mistake there.

What I have:

What I want (and have in the editing box):

The HTML of what I have in the editing box:

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