Card transactions above €1 earn you 3% cashback in Grover Cash.
The main exceptions are:
Mail order or phone order transactions
Declined or expired reservations
Refunded payments
Payments to gambling companies
Investments
Transferring money to banks
You can earn a maximum of €60 per month in Grover Cash. Once you reach the €60 limit, you'll have to wait until the following month to restart earning Grover Cash.
For all the details, take a look at the General Terms and Conditions (section 13.3).