Thank you John for your kind suggestions.
I have now my PC online via cable connection to the router.
Which is a Telekom speedport 504.
It does have Wifi. Both my notebook and my PC are linked to the speedport router.
My PC via a cable link & my notebook via a second cable link as well via Wlan connection.
Unfortunately my PC does not like working with Wlan - so the cable link is the only way open.
Perhaps the reason for refusing LAN is its location in a corner or the fact that my notebook already is linked to Wlan. I don`t know - seems to be all very complicated.
The prime matter for me is to get finally the SR1 working on my PC - till now still the yellow T.
I can do there without a Wlan Connection - for the online stuff I have my notebook running cable connection plus a stable Wlan connection to my router.
Hope this explains things better to you.