SIM card for Germany

[findnsecure]

Hello,

I travel to Germany once a year for the CeBIT. I need a SIM card for my unlocked mobile phone which has long validity so that I can retain my number (topping up via internet to extend the SIM validity is fine), has low cost high speed internet data (use of Skype and Spokn possible), low cost voice calling within Germany, instructions in english to topup and add data plan (if possible).

Any advise is most welcome

Thanks and Regards

Shailendra Bansal