Sure! Here are the sentences rewritten using "because" or "because of":

1. Kevin has failed many times because he is disappointed.
2. I had not eaten for 24 hours because I was very hungry.
3. He ate all the fruits because they were ripe.
4. He didn't go to sleep because he hadn't finished the letter.
5. He is dismissed because he is late for work very often.
6. He caused a serious accident because he drove too fast.
7. There are not many people driving cars in this city because the streets are narrow.
8. I couldn't do the test because it was so difficult.
9. I have to have my document translated into Russian because I don’t know Russian.
10. The children went to school late because they had an accident.