Oral anglais - notion "myths and heroes"

Hello everybody!
I have an oral exam in a few weeks and I would like to know if I made mistakes in my oral presentation. It would be great if someone could correct my script.
Thank you very much to spend time for me.
This is my script:
The notion I'm going to deal with is myths and heroes. To begin, I would like to give a definition of myths. Myths can be amplified representations, deformed by collective imaginary. It also can be spraded out belief groundless or legendary stories. I would like to illustrate the first definition of this notion through the theme of segregation heroes. We may wonder how common person can become myth or heroe. In order to answer this question, I will follow a framework which is a 19-year old single mother's quotation quoted by the Democratic Party and which is today famous : « Rosa sat so Martin could walk ; Martin walked so Obama could run ; Obama ran, so we could fly ».
So, to start I would like to talk about Rosa Parks and tell her story. She is the starting point of the big movement which fought against segregation in the United States of America. In 1955, Rosa Parks refused to give up her seat to a white man in a city bus in Montgomery. At that time, segregation was at its heigts, so Blacks had to respect Jim Crow Laws, which means that they were not allowed to mix with whites in public spaces and were sent to seperate schools. They were also required to sit at the back of city buses and give up their seats to white riders if the front seats filled up. For the crime of refusing vacate her seat, Rosa Parks was arrested. She was not the fisrt arrested for resisting segregation of public transportations but it was her action that became the catalyst in a movement that had already been gaining steam. That's how, on a december evening in Montgomery Alabama, a woman became an american hero.
Few years later, the Montgommery bus boycott in support of Rosa Parks brought a new powerful voice to light : Reverend Martin Luther King Junior who come to the forefront as the head of the Civil Rights Movement. His skillful language and dynamic persona became the new image of a movement dedicated to change and equality with paceful means. He organized pacefull protest marches against segregation, fought for Black right vote and mostly for any equality. Only a decade-fighting later, President Johnson signed the « Civil Rights act » and « voting rights act ». They removed institutionalized descrimination based on race. After the well known « I have a Dream » speech, where he hopes that his child will not be juged in fonction of their skin color, Martin Luther King was awarded the Nobel Peace Price.
In 2008, during the presidencial elections, Rosa Parks and Martin Luther King acts took all its meaning. For the first time in United States history, the elected president is black. This is a radical progress and a consecration for the American Black Community. Those 50-years fighting for equality were not useless. Barack Obama came to power in a state which denied decades ago people of his skin color. Martin Luther King was Barack Obama's model. This election was very symbolic. A symbol which means that segregation was over. Only with his position, Barack Obama became the new American heroe. And 45 years after the speech, King's dream came true.
To conclude, I could say that everybody could become myth or heroe. That three people I introduced was just common people before they decided to stood for their ideals. Actions made myths or heroes. And people have to believe and be based on myths or heroes in order to give themselves bravery and hop to fight for them rights. The harder the fight, the greater the victory.