Desu ne is something you want to tell them that you felt right or after the question you ask (with someone Same age, really friendly with ỏ ưith the person is younger than you)
And Desu ka? Is the word like "right?" Is the Question too. Usually they use to the person you not really friend or the person older than you (formal)
1)be smarter (study more)
2)take care of yourself (dont look dirty)
3)be polite and confident
ng alin? hindi ko alam kung ano ang sinasabi mo
Answer:
日本語が悪くて申し訳ありませんが、英語しか話せません
Explanation:
On a paper one you are more secure and extremely cautious that anyone might se it