1
May I help you?
Point to yourself for 'I', sign 'may' by bringing both 'S' hands downward, and then sign 'help' moving toward the other person. Remember to raise your eyebrows to indicate a yes/no question.
2
You may go to the bathroom.
Point to the person for 'you', sign 'may' using the firm downward motion with both fists, and follow it with the sign for 'bathroom'.
3
You may start the test now.
Sign 'you', then sign 'may' with both fists moving down together, and finish with the signs for 'start' and 'now'.