My friend keep making boring character

Hi guys, me and my 2 friend started to play the game recently and it was very fun at first when i'm the dm but a few session later their character had only 1 single personality is calm and other was alway angry but my friend who choose Personality is calm keep freak out every time something appear and the other who choose alway angry just keep trying to talk to the monster to tell them he want peace when sometime he dont know their language and they cant talk. This keep make me feel like it not roleplay anymore it is them do what they want instead what the character may want