Welcome to the TH community, @Ns sure!
I'd strongly recommend you backup all the data from the external HDD somewhere else as soon as you can access it! These clicking sounds are definitely not a good sign and usually indicate internal hardware failure. Unfortunately, this is something that cannot be fixed. You should try the external drive on another computer to see if you could see its contents from there. Another thing you should check is
how the HDD appears in Disk Management on your laptop. You might also want to try using a different USB cable and a different USB port on the laptop. Taking a screenshot from Disk Management and sharing it here would be really helpful as well.
Once you backup your files check the...