The computer is one of the most essential things. We can use computers to do a lot, such as doing homework ,sending emails. Computers are very conveniet to use and welcomed by people, but they also have disadvantages.

對比一下吧.是不是對的?我都幫你把語法改了你對比一下不同之處。不過如果是寫作的話，其實還是有更好的表達方式。你用的句式普遍比較簡單，而且突出邏輯關系的關聯(lián)詞比較少，如果有時間的話，不妨改進一下。