Can someone explain to me what happened? I'm confused. ┗( T﹏T )┛

Is there anything specific you need clarification on?

Are you talking about the latest chapter? If so... :
Basically there's traces of demon energy or whatever in the magician's tower. Someone there is secretly a contract signer (they signed a contract with Mephisto) and Gallian (green hair dude) proposed a plan for mc to fake being another contract signer to bait the bad guy. Angel dude, however, says that maybe Gallian is the bad dude