@janvierma you're doing exactly the right thing, you just need to return a redirect response from your controller.
You also want to check that your Queue Connection isn't set to Sync, which is the default out of the box, as this treats jobs as synchronous and will execute them as part of the initial request. You'll need to set up a proper queue handler like Redis or as part of your database to see the response be returned immediately.
As for the email, just set a Notification to be sent at the end of your ProcessVideos job.