Hi Goldmund,
The forum is not the right place to accuse/report someone.
Please use the report function in the future. 
To report a player, please navigate to the player's profile and click the 3 lines on the top right.

https://i.imgur.com/chKPq3x.png

And select what you want to report. You should also leave a short comment in the text box.

Kind regards,
John