Theme for English B for English 2200

This young black man is coming out of his English class thinking about what he should write for the assignment the professor asked for. This is what is happening to the young man in the poem "Theme for English B" by Langston Hughes. Although the young black man is going to a university during the 1950s, life is not as wonderful for him as it may seem. He was the only African American in his class and was not close to his family during that time which only emphasized the sense of loneliness he felt when he was thinking of what to write about. Then he thinks about things to write on and realizes that even if the instructor might not like it, he and his students (even the speaker) have so much in common that the color of the skin does not even make a significant difference. Of course, he admits that neither of them want to agree to that but it's true.
I really liked the way that Hughes wrote this because when I first read the poem I imagined the young man walking from his class through those streets, the park, all the way into his room at the Y. That imagery alone made me as a reader see the struggle he went through everyday and the two completely opposite worlds he was a part of. But as much as they were different, the speaker made them fuse together and become a part of him, to be him. When he thinks about Harlem he says, "I hear you: hear you, hear me---we two---you, me, talk on this page" and also when he is talking about his professor tells him that he is "yet a part of me, as I am a part of you." Being a black man and an old white professor is as contrary as one could get, but yet the speaker lists multiple things they have in common like "eat, sleep, drink, and be in love [...] work, read, learn, and understand life." And even the fact that they are both American puts them in a category where they could even have similar tastes in music like "Bessie, bop, or Bach." I think what the man was trying to say was that since we have constant interactions with people and even the places we go to or live in are close that we share common goals, interests and that we inevitably become part of another person just by coexisting.
Questions:
Why did the speaker say that the man was only "somewhat free?"
What did he think the white man was could/would learn from him?