Q: Should we say "The report was partly or partially written?"
A: Depends on the intention. Partial means both in part and biased. Clearly, a partly written report is one that has not been completed. If partially written, it too may be incomplete or showing partiality. Be careful.
Q: Tell me what is wrong with this sentence: "Art has ears like a donkey?"
A: The comparison is of Art's ears to a donkey, whereas it should be to a donkey's ears. Make it "Art has ears like those of a donkey" or "like a donkey's."
Q: Is a hyphen so important that it can change the meaning of a sentence?
A: Sometimes. Some solid compounds need a hyphen to express correct meaning. Consider "she brushed her coat with a horse's hairbrush" (a brush used on horses) and "She brushed it with a horse's-hair brush" (a brush made of horses' hair).
Q: How can this sentence be made clearer: "A box of flowers, gardenias, daisies, roses, was delivered today?"
A: A long appositive (here the names of the flowers) that contains commas is best set off with dashes. They will avoid two commas and make the construction more easily understood: "A box of flowers -- gardenias, daisies, roses -- was delivered today."