@remi That's a pretty common scam. When I posted my car up for sale I got loads of messages in the same format. One red flag is that they don't ask for any details and just accept your asking price without wanting to see the car or know anything about it, and they always say they can't come themselves for some reason so they'll send a friend to pick it up
The most common version of that scam is that they send you a a fake check, for more than your asking price, and ask you to wire the excess portion of the money to some third party, for "transport" of the item you're selling.
The third party's just them, of course. If you wire them the money, there's no way to get it back. Their fake check will seem to deposit, but bounce a couple of weeks later.