The PX is where the selling on this site takes place and a PX post is a post in the PX selling something. It’s what you responded to and shouldn’t. You should PM the seller directly. A PM is a private message.
But you also posted in the post. That is what you should not do. That is how the scammers knew you wanted it and started sending messages.
Speaking of those messages did you report them? If not then we don’t know about them and can’t get rid of them. You do it by hitting the report button at the bottom of the pm they sent you.
Ok- I will try to figure out how to get them back now- I thought I reported it correctly but maybe not, I am using the app and I “left” the convo and deleted it after I thought I reported them, so now I can’t find the messages