Перевод правильные, вот предложения: They set out on a long journey. Christopher Columbus was a well-known Italian explorer (можно еще добавить who completed several voyages across the Atlantic Ocean). Scientist discover new things every day. The majority of the deep ocean still hasn't been explored (надеюсь нормально что в другом времени?). There is a lot of noise from the busy traffic. Before cutting meat, you have to find a sharp knife. I will get back to you as soon as I find out the answer to your question.