In order to be able to register your trademark successfully, all formal requirements for registration have to be fulfilled. The German Patent and Trademark Office does not examine whether there are relative grounds for refusal of a trademark such as the existence of identical, nearly identical or similar trademarks. A prior rights search may help to find out if such earlier trademark rights exist and help to reduce a possible risk of collision between your trademark and an earlier trademark by e.g. reducing the scope of protection.
Trademark right is priority right. This means that earlier trademarks, including unregistered trademarks, have priority over newly registered trademarks. A trademark registration cannot exclude that earlier industrial property rights may be infringed by using your trademark. Opposing trademarks can often be detected by searches. This helps to evaluate the risks of collision between your trademark and earlier trademarks at an early stage before filing the application and putting your trademark into use.