Hey there ChaosTg,
I'm sorry to hear that your Chromecast and Samsung Galaxy S9 are not playing nicely! This can be tricky to troubleshoot on your own, so I'd be happy to help you out. First, go ahead and check out this article and follow the troubleshooting steps. Let me know if you encounter any issues or errors while attempting a specific step.
I look forward to your response, and if you have any other questions or concerns for me, please let me know.