I would definitely recommend the Einundzwanzig community and their podcasts (https://einundzwanzig.space) nostr:npub1qv02xpsc3lhxxx5x7xswf88w3u7kykft9ea7t78tz7ywxf7mxs9qrxujnc and also nostr:npub1dergggklka99wwrs92yz8wdjs952h2ux2ha2ed598ngwu9w7a6fsh9xzpc and his books. Einundzwanzig also offers courses and has a network of telegram chats that are friendly and can be pretty supportive.

Regarding places to buy in Germany I would still consider global resources like Bisq and Robosats. For newcomers, Relai app and Pocket bitcoin could be the most user-friendly resources.