1) Do you realize who you are talking to? (Correct but could use a contraction to make it seem more fluid I.E You're)
2) Do you have your English on Sunday? (Incorrect but close! Do you have your English class on Sunday?)
3) Is he your close friends? (Again, close but incorrect! Is he your close friend? Also, "Is he a close friend?" works)
4) Do you like riding on motorbike? (Close yet again! Do you like riding motorbikes? Also, Do you like riding on motorbikes?)
5) Do you know how much this car cost in 1969? (Correct, though you could smooth it out by asking, "How much was this car in 1969" or "Do you know how much the car was in 1969?"
I hope this helps, even just to get you closer to the right answer! Keep up the good work!