I think , I can answer my question myself.

After activating "Fliegen", I can choose Show Rainfall/GAFOR etc..

But I have no idea whether this is updated over the time.

I have learnt that GAFOR indications for switzerland and Austria are displayed if I have planned a route through one of these countries.
Then I get coloured lines for he GAFOR-routes incuding the D,M or O cubes.

But, even the GAFOR indications seem to disappear at the moment I touch "Fliegen". Why aren't they displayed during Flight ?
I know, Web access is limited but wouldn't that be a useful feature to have updates in-flight if available? Maybe I simply have to activate something.