This is just an analytical question, not blaming nor scapegoating:
1. Who do you think have biggest responsibility on making those prices fall and keep down? the big sharks or purely the market?
Nobody is having any responsibility of dumping or pumping the coins. If someone is going that then they are doing it artificially and at their own will. Now the thing is we can not stop that from happening as we are surfing the decentralised market based on the public leader, anyone can fiddle with it if they have enough funds! If the prices are falling or even increasing then it could be both whales or natural market.
2. Whether the ones who made it fall is the same one who keeps it down or not?
Refer to the first question's answer and it makes it clear that it depends on the situation. Also, I am sure that if whale are making it drop then they will let it grow naturally so that they can gain profits.
3. And what to do make them bounce again, although slowly?
Off course purge the more volume into the market which was void before due to mega dumps!