Thank you for the tips but:
I do not think that it is a DNS issue as the DNS seeds are retrieved else I would not see the IP address.
I do not think that it is a FW error as the nmap show the port as closed and not filtered.
C:\Users\rrunner>nmap 126.96.36.199 -p 19333 -Pn
Starting Nmap 6.49BETA6 ( https://nmap.org ) at 2017-04-11 23:50 Central Europe Summer Time
Nmap scan report for yurika.gransy.com (188.8.131.52)
Host is up (0.012s latency).
PORT STATE SERVICE
19333/tcp closed litecoin
Nmap done: 1 IP address (1 host up) scanned in 0.66 seconds
This would mean that the end point was reached but the port is closed (service not running).
Same result for all the other nodes which I tried out from google search…
My FW is blocking only all incoming TCP connection and this would be a outgoing.The LTC wallet can connect to the ordinary network on port 9333. I can not connect only to the testnet of Litecoin…
Please has anybody more hints what could be wrong ?