So noone wants to trade my for your Mount and Blade Warband: Steam ?
Why would anyone? Given that the cheapest Mount & Blade: Warband has ever sold for here is $4.99 ($3.99 bundled) and that the regional price loophole has been closed for more than a year. But somehow G2A has a user selling keys for that game at $1.55...
Then if you check his profile, tons of his keys for that game are invalid (not surprising). I couldn't find one sold that even received a positive; found 7 that were no good in his negative ratings.
Have you even checked to see if the code works?
Not to go into the idea that Mount & Blade Warband has never been bundled for Steam, so it's not like anyone will have extra codes for it just laying around. Instead, to trade you, you are asking them to pay $3.92 for a Steam key (best current sale price according to ITAD) to trade you, that you likely bought for $1.55.
Why would anyone want to do that?
My suggestion for you is to check the key here. Find out it is no good. Then see if you can get a refund from G2A. (Good luck!)