Hello, please provide uncropped (whole screen visible)/unedited screenshot evidence of your interactions with this user. If you have access to these from the original chat window. Upload them to an image hosting service (imgur, for example) and post the links here.
Please also provide Uncropped and Unedited screenshots of your ENTIRE chat with the user from this page -- https://help.steampowered.com/en/accountdata/GetFriendMessagesLog -- Please find them on a web browser and hover your mouse over the name of the user you are interacting with so we can see the URL at the bottom left corner of the screen. Then upload them to an image hosting service (imgur for example) and post the links to your evidence of screenshot here.
Example- should look like this - https://imgur.com/MjGyin8