You may write as many stories as you wish per play session - some have even written as many as twenty to thirty different stories.
And you're more than welcome to write in German. The support for umlauts and non-English characters may be a bit hesitant, but otherwise it should be okay :)
I'm so sorry to hear that, I'm not sure quite what may be causing that.
If you're located in the Northern Hemisphere it's possible the connection may be timing out (servers are located in Australia), so may take a look at it sometime this week.
I believe that may be the case, I'm so sorry to hear that. At this point I'm unable to transfer (or split) the server to a more accessible location, but I would be more than happy to offer a full refund if you wish :)