I have to create a game so that the game has 3 levels each level has character who is a kid he should walk along the road and has to answer simple questions.
If I were you - I’d check out the resources and tutorials here on Unity3D.
Then, take a look at unity3dstudent.com - its great to get for getting beginners off the ground.
good luck with your game.
To create a simple game you make some graphics and scripts.
alternatively you can hire somebody