revolution slider won’t autostart on firefox, except if you click “Giriş” on top menu (when appears) while page loading, video starts perfectly. This behavior works only click while loading, if you click menu after page load video doesn’t work.
The problem is that your video has sound. Since last months browsers like Firefox are blocking autoplay for videos with sound (even if you set “data-volume” on Revolution Slider video settings). On this case we recommend you generate a new video without sound. You can use a tool like https://www.kapwing.com/tools/mute-video or any other.
Please try that and let us know if you need further assistance.