I was quickly signed by the postal courier. Do I have to pay hundreds of dollars? He didn't ask me to sign for it, just asked me to send it to the post office, where he signed for it for me.

It is illegal to sign for your express delivery without your authorization. According to Article 75 of the Postal Law of People's Republic of China (PRC), if a postal enterprise and its staff commit one of the following acts, the postal administration department shall order it to make corrections and may impose a fine of less than 50,000 yuan; If the circumstances are serious, the business license of postal enterprises shall be revoked:

(a) unauthorized opening of mail or postal parcels, or unauthorized inspection of the contents of mail or postal parcels;

(2) detaining or intercepting mail or postal parcels without permission, or opening or inspecting the contents of mail or postal parcels without permission;

(3) Receiving and sending mail or postal parcels without permission or signing for them without permission, or receiving and sending mail or postal parcels in violation of regulations.

So you can complain to the postal administration and ask for compensation. As for the specific compensation, you need to consider the value, loss and inconvenience of your express delivery. You can negotiate with the courier company or seek compensation through legal channels. I suggest you consult a professional lawyer.