Traded Max Payne 3 (DE) away. Trader wants to report me because there is no English.

he has every right to report you. Most (DE) games have ONLY german launguage.

No it is not if it is DE then it completely DE.

If the item isn't as you described it and doesn't contain English, the other person should receive reimbursement and has the right to report the incident.

here

Is there no language tab under: rightclick in steam->properties?

If I buy something labeled made in china in a store, eat it and return the wrapper later saying it wasn't made in America thats my fault.

You told him what it was and explained it, he bought it, his fault.

Whoever buys a censored game by his OWN will, is pure idiot.
Period.

PC: All Versions****: English, French, Italian, German, Spanish, Russian, Portuguese (Brazil), Polish

****No patches or updates are needed for any of the supported languages on PC. All languages are included with the shipped (or downloaded) game.

From: http://support.rockstargames.com/hc/en-us/articles/200153716-Max-Payne-3-List-of-supported-languages

Language can be changed with commandline: -language english (options in steam).

Its like this: The Steam Store page for the german version says "Low Violence", but also states its playable in German, English, French, Italian and Russian. If it really doesn´t work, its neither your fault nor his fault and you have to involve the Steam-Support as they are stating false info in their Store.

There are three posibilities ways to change the language of a game: In some games you can choose it in the ingame-menu. For some you have to change it in steam with rightclick->properties->language.. but some others are using the laguage of the steam client itself. I´m a German user with a ROW-Version of the game and just checked and the first two options don´t seem to apply here, so it might be that he has to change the language of his steam-client.. not sure why he would have a german steam client if he complains about german ingame-menus though.
If this doesn´t work, Steam-Support has to work it out.

if it happened within the trade window then he knew what he was getting into. i think you'll be fine.

wait you said it was in english language but it wasn't? If so that's pretty sad, though the person who ''traded'' for it should've done some research

You should have read my thread first
Also Max Payne 3 has English language included, Steam says. Also if you want to know more about the cut, visit Schnittberichte.com.

You said you have the DE version, you have not lied about the product you were offering, I see no reason for you to get a ban.

Tell the person to mess with the ini files, you can mess with the ini file to turn it into english and remove censoring.