Dear Teachers
A.- How are you doing at school / at college / at university?
- How are you doing with your study?
- How's your study going?
B. Whenever you meet sad things, just cheer up and be strong. And then you’ll overcome them.
Are A & B natural?
Thanks a lot
Namsteven
A.1. is fine.
A.2. If this applies to courses in college, it should be "studies". Using the singular refers to a particular work, such as a research project.
A.3. How are your studies going? (same reason as A.2.)
The beginning of B is not terribly natural, IMO.
Whenever you have troubles/problems...
Whenever you see things that make you sad...