I want to ask you all, why if bitcoin price goes down, altcoins price also come down, what is alcoin-price bitcoin, please give me your answer.
Altcoin stands for alternative to Bitcoin and is used describe any crypto currency that is not a Bitcoin. If the price of Bitcoin is falling then altcoins usually goes down too.

because every bitcoin decreases Altcoin price always follow its movement and as it is now Altcoin price also decreased following bitcoin movement because bitcon has decreased a few months ago hence even though bitcoin price decreased a few months ago and finally now Altcoin always follow its movement