Don't make your character say the same word over and over again, use some synonyms for example.
That was good thinking, it's good design will definitely get us to first place. After that we can go to this good place which has some pretty good food. Good job everyone!
Some ways you can fix this is by having it so they say different words that have the same. Instead do something like this.
That was some smart thinking, it's new design is amazing and will get us first place. Do you think after that we can go to this restaurant and get some awesome food. Great job everyone see you tomorrow.
With writing like that it won't get annoying to the reader that your repeating the same word over and over.
Now they way a character speaks can also effect a character. If the have an accent a spelling fix well help. Not having every word spelled differently will let the reader know that you're not a second grader typing out a story blind folded or from a foreign land using an English keyboard for the first time.
Also helping with this is having the character speak differently is using different vocabulary like a howdy, hey, or greetings instead of a simple hello. Listening to podcasts or watching movies can help with this. Don't listen to music because most of the time they say Ya, kay, and Fo.
Don't have them talk for to long, or else the reader will get bored. Like maybe a sentence or two will help out with writing and don't use to many adjectives in the sentence unless they are essential.
Don't use the word "said" all they time. Use exclaimed, shouted, and other words that I can't look up at the time because I'm eating a sandwich.
When a character is excited or mad don't use caps lock or wattpad's bold feature. Use exclaimed or shouted and add an exclamation point.