We can learn a lot about the character Mitch throughout the play through his dialogue (his dialogue with Blanche says a lot about his character too. We can easily get the vibe that he is not particularly bright or ambitious in that he is very clumsy and is often teased by Blanche (such as when she speaks to him in French which she knows he will never understand, also when he uses bad grammar and slang “Kind of on your high horse ain’t you… I oughta go home”). He tries to behave as a gentleman to Blanche though, being very polite to her and trying to meet the social standards of what it was to be a gentleman during this time period. (Ie calling Blanche Ms DuBois and the beginning and acting awkwardly respectful)
We learn that he is also a lonely person through his dialogue who wishes to make his mother happy. We can see this in the fact that we hear of his mother a lot but never actually see her. She is just constantly referenced. (such as at poker night when they talk about the custard Stella sent to his sick mother)