Google Pay is now available in Germany with support for four local banks: Commerzbank, Comdirect, Wirecard and N26. You should be able to add all MasterCard and most Visa cards. Two more banks (LBBW and Revolut) will be supported soon. As for where you can go, supermarket giants Aldi Sud, Kaufland and Lidl are ready for you, as are retailers MediaMarkt and Saturn, DIY chain Hornbach, along with McDonalds and Adidas. Aside from brick and mortar stores a number of apps and websites support Pay too. Source (in German)
Source: https://www.gsmarena.com/google_pay_arrives_in_germany_with_four_banks-news-31877.php
