LOL, a scammer:

That usually happens, a scammer add you. I talk to they to have some fun, i could not go ahead to troll this one anyway:

14:52 - Gaben Newell (TR): I want CS:GO weapons your have ??? I have knife
14:52 - The Trader: no, but i can try to get something
14:52 - The Trader: wich knife do you have and what do you want?
14:53 - Gaben Newell (TR): yes
14:53 - The Trader: wtf
14:53 - The Trader: yes what?
14:53 - Você aceitou a solicitação de troca de Gaben Newell (TR).
14:54 - Gaben Newell (TR): FU#K YOU NOOB
14:54 - The Trader: lol
14:54 - Gaben Newell (TR): FU#K YOU NOOB
14:54 - Gaben Newell (TR): FU#K YOU NOOB
14:54 - Gaben Newell (TR): FU#K YOU NOOB

EDIT: (profile removed)