Are you using hive.blog or what? I doubt it has much to do with the backend. More likely it has to do with how the interface itself is formatted.

Maybe look at the source for the webpage, if you're comfortable with that. Your content might just have width dimension higher than whatever element is holding it.

As for your uploading troubles, I almost never put images in my posts. I don't really know that much about the process, but in some interfaces I'm pretty sure you can upload images from your local storage via the provided editor.

Images aren't stored on the blockchain these days, of course, but most interfaces do some image hosting.