Theory:

     It took several camels from the village to remove the property Vijay Singh had acquired. He returned much of it to the rightful owners. He went especially to the old woman, thanked her for her invaluable gift, and asked for her granddaughter’s hand in marriage.
 
     Thenceforth, Vijay Singh was more careful about boasting. It is said that no traveller was ever troubled again in the Haunted Desert.
Explanation:
 
Vijay Singh proved his intelligence besides being a wrestler. Though he was a powerful wrestler, he weakened the ghost psychologically and won it wisely. He brilliantly tackled the ghost, unlike others. At last, when he won the challenge and restored all the looted things of village people.
 
It took several camels from the village to carry the looted items back. Vijay Singh handed over much of the stolen items to the rightful owners. He then met the old woman who gave him the egg and salt's lump during his journey. He thanked her for the invaluable gift, which saved his life. And then, married the old woman's granddaughter in return for her help.

From then, Vijay Singh was cautious with his words. He never boast highly about himself. And, most importantly, no other traveller was harmed or killed by anyone in that haunted desert.

Though Vijay Singh's boasting habit landed himself in trouble, he tackled it successfully with his knowledge. Vijay Singh' efforts not only saved himself but protected people from the ghost, especially travellers after then.
 
Meaning of difficult words:
 
S.No
Words
Meaning
1.
Acquire
To get or buy something
2.
Invaluable
Something extremely useful
Reference:
National Council of Educational Research and Training (2006). A Strange Wrestling Match: Indira David (pp. 43-51). Published at the Publication Division by the Secretary, National Council of Educational Research and Training, Sri Aurobindo Marg, New Delhi.