"I'm worry about your health" Formal : 당신의 건강이 걱정됩니다. Informal : 너의 건강이 걱정돼. "Please have some rest" Formal : 휴식을 조금 가지세요. Informal : 조금 쉬어.

nearly! "I'm worried about your health, you should take a (some) rest" We use should when offering advice. Take a rest means one rest. Take some rest means to take a few days rest, or some time off work. I hope that helps!