If your ping is normal with other servers, e.g. those of speedtest, it comes from a problem on the route between swisscom and the server.
If you can get the server address and do a traceroute (tracert*) that will clarify the situation.
*windows key + r
cmd then enter
tracertserveripaddresswithoutport
This type of problem is common for games like League of Legends or others.
Unfortunately, this is a problem independent of the swisscom network. It is often after leaving the swisscom network that one of the gateways is overloaded, causing an increase in latency time.