Your English seems clear, I wish my German was half as good.
I assume you are using a German version of Quicken. I don't have a specific answer to your problem but perhaps can give you some generic advice. Quicken uses what we call a ticker symbol to request a stock price quotation. I've seen a few reasons for stock quote updates to stop.
1) The ticker symbol for the stock has changed (usually as a result of a corporate acquisition). This is solved by finding the new symbol typically on a financial news service. I tried looking for a price for BASF using Google Finance (from the US). Google doesn't have symbols for BASF Corporation but shows "Private" instead. I don't know if this just means it isn't traded on a US market or if BASF went private. If the later, that would explain why you are not receiving quotes.
There's some kind of a problem with the server providing the quote. If this doesn't fix itself, resolving this requires contacting support, presumably by the German distributer.
I hope this is of some help. Post back if you need clarification.
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