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How do you identify the TYPE of grammar error.?

I know what is wrong with these two sentences bu I don't know what type of error they are called, can you help me?
1.Those who the Nazi did harm to have no way of forgiving him.
(in this sentence i think it should " those whom the nazi harmed")
2.And i couldn't find anything wrong with this sentence: Since Germany's economy was near worthless, people were desperate for a strong leader?
Easy best answer for all you people who have the names of grammar rules memorized!

1) "Who" should be "whom" because it is the object of the preposition "to."
2) "Near" should be "nearly" because "worthless" is an adjective that must be modified by an adverb.