CSS to hide progress bar, full screen, pause button

The best place for the CSS would be in the style.css file of a child theme. If you are using Jetpack there is a place to add custom CSS. I hope this helps.

It might have something to do with the video ratio and the measurements defined in the configuration setting of the video.

If you share a link where the video is placed I might have a better idea.

The link is no redirecting to another site which is not using Flowplayer anymore. Did something change?

It seems the video dimensions are not defined correctly. You want to define the width “1920” and height “1080”. You could define the maximum width if you wanted to but should not be necessary as the video is responsive.

Your video should be optimized. The 25 sec video is about 60 MB. One of my videos which is 30 long is only 4 MB. You can see how much you can optimize it.

Check out Flowplayer Drive https://flowplayer.org/pricing/ It hosts your videos and automaically generates all of needed video formats for best browser support and the thumbnail. Try it out and see if you see the difference in speed.