If the other party is already using the trademark before the date of application by the applicant, but has not registered it, the other party can file an objection during the announcement period or after obtaining the certificate. If an invalidation application is filed, the applicant's trademark rights may be canceled based on the other party's prior right of use, and the other party obtains the exclusive right to use the trademark. Of course, this is only if he has a good understanding of trademark law, or if he consults the agency for suggestions, but he will need to pay for it. So let’s see if he pays enough attention to the trademark. If the other party chooses not to object to the trademark, or the trademark is declared invalid. Then you can use it. Or negotiate to see the strength of the company. If that doesn't work, then register another trademark. To be on the safe side