Please take one additional screenshot of your interactions with this user. Take it from here - https://help.steampowered.com/en/accountdata/GetFriendMessagesLog - and when you take it, please do so in a web browser rather than Steam client and hover your mouse over the name of the user you are interacting with so that their profile URL displays in the lower left hand corner of the screen (and again, remember not to crop or edit them in any way). Then upload it to an image hosting service (imgur, for example) and post the link here. One screenshot formatted in this way should be sufficient, and it will will help us prove that the conversation shown in your other screenshots was indeed with the reported user.
https://imgur.com/a/EedfCou - Chat1
https://imgur.com/a/B7arVtW - Chat2
https://imgur.com/a/hTlUsHx - Chat3
https://imgur.com/a/Aic30Cc - Chat4
https://imgur.com/a/1voJ24G - Chat5
https://imgur.com/a/2UJytUs - Chat6
https://imgur.com/a/MINwOGf - Chat7
https://imgur.com/a/VtFTYDG - Chat8
https://imgur.com/a/fzlQyEX - Chat9
https://imgur.com/a/FKYFY1P - Chat10
https://imgur.com/a/E5AZDcm - Trade
Edit: paypal images removed for privacy of reporter.