At what price could i sell them ?

Maybe, if you find someone who wants them.

I'd say that all of those gifts should buy you a knife purely on the fact that they're gifts, not keys.

don't know I'm afraid - but that is a lot of bullying games :)

i bought some bully's idk why :/

I highly doubt that anyone would accept these gifts for a knife. However, you could trade the gifts for keys and then the keys for a knife.

::/ yeah thanks

i dont think so, maybe some cheapest boreal forest around 40€ with ton of luck ;)
am like your trading partner (if), only rlly few games from inv are interesteing (basically Bully and BF, BattleBlock, AoE :D) and if iam your trade partner with knife, i wont pay knife for this inventory, so i rlly think nope