Thanks for all the input.
I checked the speed test -> OK full speed 100 Mbps
I checked with my mobile phone -> much faster Download > 500 kb/s even if mobile connection is low at home !
Switched back to wlan -> 20 kb/s

So the PGMusic Server seems to be OK but my WLAN doesn't work with PGMusic server . Other Downloads from other websites are working fast as usual.

So current situation is :
- Download at PGMusic with MacBook Pro and WLAN -> 17 KB/s -> 2 days
- Download at PGMusic with MacBook Pro via iPhone sharing -> 500 Kb/s 1h
- Download check at Apple 10GB with MacBook Pro and WLAN -> 15 min -> normal
- Try to download from PGMusic Website via Browser -> 17 Kb/s -> 2 days

So I get at any server full download speed via Browser with WLAN but not at PGMusic.com
But mobile connection and Install Manager seems to be normal.
So in general it seems to be related to WLAN but on the other hand all other downloads works normal.

Next I will check
- my settings in the router (Fritzbox 7490) -> disable IP6
- try other computer

Very strange behavior .

BR

Stephan