Hit:1 http://ch.archive.ubuntu.com/ubuntu xenial InRelease
Hit:2 http://ch.archive.ubuntu.com/ubuntu xenial-updates InRelease
Hit:3 http://ch.archive.ubuntu.com/ubuntu xenial-backports InRelease
Hit:4 http://archive.canonical.com/ubuntu xenial InRelease
Get:5 http://security.ubuntu.com/ubuntu xenial-security InRelease [94.5 kB]
Fetched 94.5 kB in 0s (160 kB/s)
Reading package lists... Done
Personally I'd rather suggest on installing and using Synaptic as GUI package manager. It is much easier to use and more straight forward than the software center stuff.