Hello Yasin_Arslan,
To help us better assist you, we'd like to confirm a few details.
1. Does this happen when watching or playing videos from a specific website on those browsers, or does it happen with multiple websites?
2. Is this happening with all videos, or only certain ones?
3. Is the issue only with audio from videos? In other words, does other audio or music play as expected?
That information will help us plan how to proceed.
Please also check out this link, which has some information that can help if you're experiencing audio issues with an HDMI device: Connect to HDMI from your Mac
If your HDMI device isn't receiving audio
If your HDMI device isn't receiving audio from your Mac:
* Choose Apple menu > System Settings (or System Preferences), then click Sound. In the Output pane, make sure that your HDMI device is selected.
* If you're connecting from a Mac mini, disconnect any audio device from your computer's headphone jack.
Thanks!