For the purposes of this question, I will assume that I “met” Lincoln while he was alive, say in early April of 1865. He does not know how Reconstruction will happen or how the US will turn out.
The first question I would ask him is what he plans to do about the status of the freed slaves in the South. I would want to ask him what political, economic, and social rights and opportunities he plans to give them. What I want to know is if he would allow blacks to vote and to have legal equality with whites.
The second question I would ask would be about his personal qualities and his presidency. I would want to ask him what he thought were the best and worst aspects of how he had done his job up to that point. I would want to know if he felt that he had managed a “team of rivals” in a way that showed political genius. I would want to know what things he felt that he should have done better.
These questions would give me a great deal of insight into what kind of a person he was and how he saw himself and his country.