@Valentina-Lola0 If it was the guest who wanted to cancel, why did you do the cancelling on Airbnb? I'm afraid that this guest made money at your expense. When a host cancels, Airbnb refunds the guest 100% and often adds 10% for the inconvenience. That's why Airbnb imposes penalties on hosts who cancel.
You can stop the harrassment from this guest by flagging his messages (hopefully all his messages are on the Airbnb messaging system) and / or his profile. Use the small flag icon to do this.
If the conversation about the guest wanting to cancel is on record with Airbnb's messaging, contact Airbnb to explain the situation. Here's how: