I signed a property power of attorney with the developer for three years, and the partner wants to do it himself. Can I sue my partner?

Yes If the partner wants to do it himself, if he violates the contract, he can directly sue the partner in court. The people's court is the national judicial organ in People's Republic of China (PRC), which independently exercises judicial power on behalf of the state in accordance with the law, and is not interfered by any administrative organ, social organization or individual.