Theory:

     Early the next morning a man going to work thought he heard a groan as he walked along the top of the dike. Looking over the edge, he saw a child clinging to the side of the great wall.
 
     “What’s the matter?” he called. “Are you hurt?”
 
     “I’m keeping the water back!” Peter yelled. “Tell them to come quickly!”
Explanation:
 
As previously stated, despite finding it hard to close the dike hole with his small hands throughout the night, Peter did not abandon the task. The next morning, a man walked along the top of the dike, passed by the path where Peter was and he heard a groaning sound there. At last, someone came to help Peter and everything seemed to be back to normal.
 
He observed Peter clinging to the dike's side from over the edge. The term 'great wall' refers to a Holland dike and specifically the place near where Peter was,  in this context. The man then approached Peter and inquired as to what was going on, assuming Peter had fallen or injured himself. Peter responded that he was blocking the opening to keep the water out of Holland.
 
He then screamed, pleading for help to cover the seawater hole. As a result, the gentleman was able to comprehend Peter's sacrifice and how Peter (small kid) had saved their motherland the night prior.
  
Meaning of difficult words:
  
S. No.
Words
Meaning
1.
ClingTo hold on to something tightly
Reference:
State Council of Educational Research and Training (2018). English Standard-10. The Little Hero of Holland- Mary Mapes Dodge (pp. 183-185). Published by the Tamil Nadu Textbook and Educational Services Corporation