This is a bit tricky. Your answers are sort of right, but you have assumed constant accelerations (that is, you have drawn straight lines). I see no such statement in the question. Indeed, the position-time graphs don't look like parabolas, suggesting the v-t graph should have curved lines. As against that, drawing accurate curves is going to be hard without a lot of detailed measurement of the given curves.
So let's pretend acceleration is supposed to be constant.
Your first graph is fine, except that you need to think about the actual velocity at time 0. What would you say that is, looking at the position-time graph?
2nd graph is ok.
For the third, what is the velocity at time 0? What is the velocity a bit later?
