I forgot to include the following sentences. I made the changes you told me.
Isnt't the subject missing in sentence? Is it possible to use the conditional in sentence 2?
I divided sentence 3 into two separate sentences, as you suggested.
1) On the stone was written that he who pulled the sword out of that stone was (would be?) the new king of England.
2) On the one hand, he had to fight against many enemies from other lands. On the other hand, some noblemen of his own court caused trouble because they didn't want to obey a young king. (his kingdom was troubled by the clash with the noblemen of his court..?)
1. would be (not was)
2. fine (delete all in parentheses)