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Hi Li Shing and Welcome to MySwissAlps!
The Swiss Travel Pass covers rail travel in Switzerland only. You will need to buy a ticket for the German part of your trip. Please see the Swiss Travel Pass page here for more details and a map of the areas of validity. Seat reservations are not required In Germany or Switzerland but for long distance trips I recommend getting one.
Here is a link for train tickets between Germany and Switzerland for you to read as well. In your case the Swiss Travel Pass validity will end at Basel train station; after that you will need a ticket for the rest of the trip.
Regards,
Lucas