1) The time depends on what the lab wanted you to do. It will tell you in the procedure when you are supposed to considered a reaction to be complete and you just measure the time for that to happen.
2) Most text books say that increasing the concentration of one or more reactants will increase the rate of the reaction. To prove this with your data you need to show that when you increased the concentration of one of the reactants, the reaction rate did increase. The results of this experiment are not enough to make a general statement since the experiment was not on a large enough scale to diffidently prove anything. (you could have been testing the one exception or had a error in one of your trials)
I hope this helps. Let me know in the comments if anything is unclear.
(The concentration of one or more of the reactants will increase the rate of the reaction. This is explained through the fact that all reactions require collisions that have certain orientations and a minimum energy level. By increasing the concentration of one or more reactants, you increase the number of collisions which increases the rate since requires collisions in order to occur.)
