Hey all! First post, sadly not a happy one haha

'06 r53

recently my brake fluid went below one of the lines for the clutch pump, after filling it back up it was a little spongy but was working fine for about a week.

then almost home from work my clutch pedal fell to the floor completely, after messing with it a little bit I was able to shift into second gear with a squealing sound and clutch pedal up (I forget in what order!) and made it home.

now when I start the vehicle I get this sound:

 

If the b-fluid level dropped below the clutch line inlet, you need to bleed the slave cylinder. Did you force it into gears? Judging from the video, the force you apply on the pedal is normal now?
Start the car on a flat low-resistance surface, release the e-brake, go into 1st and fully depress the pedal. Wait a bit and see if the car starts moving forward.

 

Sure sounds like a release bearing fault to me. Nice shoes by the way.

 

+1. That's just about exactly what mine sounded like after it blew up.

 

In your case air got definitely in the clutch line and slave cylinder doesn't go out properly.
Here is the video how to bleed it