Battery empty after repair oil cooler

Hey guys, I had my fat from 3 weeks ago until 1 week ago in the middle of Germany in the repair. On the highway the oil cooler went through me, in the entire cooling circuit only oil majonaise. Thermostat, oil cooler, coolant bridge seals, heating circuit control valve, water cooler, water pump, timing belt, new coolant and new oil were changed. Last week I brought the fat back to Cologne (300 km). Yesterday, after 1 week of service, I was a small round through the I don’t know what it was like at the start. I would say that I didn’t notice that it was hard to start. The battery is only a few months old by the way, and thanks to the long distance (700 km) it’s usually steep. Before I want to go shopping, the car doesn’t make any noise. Even the ZV didn’t open up. My question: Can the workshop do something bad? We don’t have mass connection to the generator again, do we? Thank you for your answer.