I had commented this on another site a few weeks ago.
Just like what others had said. You really don't need to care if your characters have personality in the way they are talking. But here's a couple method that I found through experience, especially when your character needs to talk twice in a row.
First Method: you put a whole action paragraph before the dialogue.
When B was browsing through the social media in peace, the door suddenly opened following A barging in and shocking B in his comfy position.
"Hey, you hungry? wanna eat together?" A asked in enthusiasm.
"Hmm... Sure"
B slowly closed his phone and yawned slightly.
"Where are we eating?"
However, before A even said anything, B interrupted her.
"Just in case, I'm not the one paying right?"
"..."
As the two stared at each other for a good second, A rolled her eyes and sighed.
"Stingy bastard, fine I'll pay"
But then, A crossed her arm and shot him a stern look.
"But you must help me with my study"
"Sure~~ sure~~"
Having successfully save his poor pocket, B put on a happy smile.
"So? where are we eating?"
Second Method: you skip the dialogue and summarized it inside the paragraph.
"Hey... I get that you're paying... but aren't you too shameless to only buy these cheap food?" B was left speechless at his friend.
But soon, B quickly regretted what he just said when he heard A's rambling about how it's not shameless when compared to himself.
A even began listing every single shameless thing that B had done in these past few months.
B's face quickly turned red tomato with every line uttered by his friend. And in fear, B quickly apologized to her and begged A to stop talking.
The girl snickered in delight at her friend's poor state. But after feeling a little guilty, A chuckled and said that she was joking before ordering more food for them to eat.
However, the pain of A's words was too piercing for B. So he quickly declined the ordered food and gave an excuse about going for a diet.
This in turn make the whole eating experience quite awkward for the both of them.
Third Method: you use the version of 'he said', 'she said', 'I said'. However, use it sparingly, cleverly, and make sure it has flavors.
"Hey... didn't we already had an exam about this a few days ago. Why do you still want to learn this?" B glanced at A with confusion in his eyes.
"W-well... let's just say I kinda... forget to study?"
B gave out a long sigh and said.
"You... did you get told to redo the exam by the teacher?"
B voiced out his pity for her.
"I get that you suck at math. but damn... this is..."
"H-hey! I just forget to study ok?! Don't you dare think that i'm stupid!"
But when A saw B's pitying look turning even stronger, Her face became redder and redder as she started to spout all kinds of things.
"S-so what? Even if i'm dumb. I'm still pretty! So i'm a pretty dumb student-... wait a minute..."
"A-anyway can we not focus on that! We had an agreement" A was so flustered that she couldn't even look at the boy in the eyes.
'Aagh... this is embarassing' She thought to herself as she caressed her already hot cheek.
B grinned at the active girl sitting beside him.
"don't worry, if I can't make you pass this reexam, i'll willingly be your servant for the whole month-"
However, B suddenly stopped when he saw A's eyes glint in wickedness.
"...Eee why are you looking at me like that"
B gulped awkwardly.
"F-forget it, I take my words back..."
"Ehh?! But why?!" A asked in great disbelief, she felt betrayed.
"What do you mean why?! I dare you look at your grinning mouth and ask that again!"
There are tons of ways to make the dialogue clear for your readers. but honestly, it's not even a must if each characters are clearly distinct from another. Yours is already good bro.
