ABC fast, or ABCD slow

Even though Im not expert I would say thay you certainly need to at least try to solve D. Most of experts that I know are usually solving them, and even if reaching expert is possible without such skill its still important just for depth of your knowledge itself.

Just focus on solving problems, if you have been stuck (AKA no more ideas) for about 20 minutes, move on to another problem.

You don't have to solve D to reach expert, many experts just speedforce ABC. Based on what I saw, experts usually solve C in about 20 minutes, so it shouldn't take that long either.

Try upsolving Div.2 contests and aim to solve ABC as quick as possible, if you still have time left, try solving D. (Virtual contests are also an option).

ABC fast is enough for expert.

I love Feli.

You need to if D is easy.

However, ABC in every contest is a promise to expert.

ABC fast or ABCD

However, there's another way, if you like div3! all ProblemSet — 1 will be enough

what topics do i need for C?

Solve all the problems to be sure