Dear Alex,

 How are things? Hope you and your family are always healthy. I really apologize for not writing to you soon because of hectic studies. Now I am going to reply to your last letter.

 Regarding your question, I would like to say that there are many ways to keep your body fit. Firstly, you should do research about workout plans and choose the most suitable for you. Secondly, you should follow it seriously. If you do not have any motivation, you can make some "challenges". Each time you finish a challenge, you can receive a reward. Thirdly, you have to have a diet. You should eat nutritious lentils, like walnuts.

 Now, it is time to go.

 Cheers.

 Vu