IANAL and this probably differs a lot per country. But typically you do not need to register a trademark, you only lose it if you do not actively defend it. So a small business could still sue Lieferando when they take your name. However, I think most small companies with thin margins would find the idea too daunting.

For the usual case of "Ristorante Napoli #239878", "Bangkok Asia Imbiss #9999" and "Taverna Rhodos #4711" you cannot register a trademark because those names are usually not unique and often reference generic place names or stuff like that.