i think you should add, why you think you are incorrect

Because I have the Ai opponent attacking before me, and when I check the stats the characters have lower overall speed  than my characters.

That is also taking into account any overall speed bonus the leader may offer.

did you attack friend or clanmate? how do you know the speed of enemy team?

i rly don't know, how to find out the speed of enemy team (if it's not clanmate, friend or you are at same chanel so you can ask)

he had probably just more speed than you

You are correct. Who ever fills the bar first gets the turn!