I have a flight on weekend, from Germany to India via Doha, with a halt of 8 hours at Doha. Can I visit Doha within this time? I have an Indian passport and EU work permit.
No, you can not.
Indian citizens require a visa to enter Qatar, and this visa must be obtained in advance (Citizens from a small number of countries can obtain them on arrival, but not India).
The only exception this is if your layover is greater than 8 hours and you have a prearranged "Stopover Paid by Carrier" (STPC), where the airline provides you with a hotel room during an extended layover. In this case you may be allowed enter the country in order to go to your hotel, however even then it's at the discretion of the immigration officials and there's no guarantee that you'll be allowed pass through immigration.