Why don’t the cullens like the ma sói at first?? ( and vice versa) I mean they have a treaty and they don’t kill humans so what is their problem?

The ma sói don't like the Cullens because as werewolves/shapeshifters, they have an intrinsic animosity towards all vampires. They smell vampiric venom and instantly think "enemy". Even though the Cullens don't hunt humans, the ma sói think of them sort of like a ticking time bomb. The ma sói who don't like being ma sói also blame the Cullens' presence for triggering their phasing and the negative effect that's had on their lives.

The Cullens mainly dislike the ma sói because they're picking up on this animosity and reciprocating it. They also feel that the ma sói smell weird - kind of like a wet dog smell - and they worry about ma sói being a danger to Bella because of how they can't always control their phasing when they're new to being a werewolf.