Creating a subtitle file

I'd get rid of the title on the top line and just use webvtt

The timing should be start HOURS:MINUTES:SECONDS.milliseconds --> ending at HOURS:MINUTES:SECONDS.milliseconds

Your timing is incorrect. 

Your first line starts at 3 minutes and ends at 7 seconds. Your second line starts at 8 minutes and ends at 012 seconds. 

Instead of manually typing the captions in a notepad you could bring the video into Storyline and then copy and paste the captions. And then export the captions.

Some people upload the video to Youtube and let them do the captions automatically. It's free and you can make edits. 

If you're doing a lot of captions it's worth using a service like Rev since the cost is nominal compared to the manual work.

Here's how to create captions in Storyline.

https://360.articulate.com/review/content/0d4aa10d-409a-485b-bd7d-0a4586e95659/review

Tips

https://community.articulate.com/articles/storyline-360-creating-and-editing-closed-captions-with-the-built-in-editor#:~:text=Select%20a%20video%20or%20audio,media%20clip%20already%20has%20captions.

I always use Storyline for creating CC files

Subtitle Edit is a powerful tool to create CC files.

Thanks a lot for all your tips and advice! I'll try them right away.

Best wishes, Rebecca