I am very confused with the current market, because when the price of Bitcoin down most Altcoin prices go down too, but when the price of Bitcoin increases only a few Altcoin that increases the price, but some are actually declining because the price of Bitcoin increases, so what affects the price Altcoin? and better invest in Bitcoin or Altcoin? please make your opinion and the reason.
You seem to be mistaken over here a bit. When the price of Bitcoin goes up, other coins along with bitcoin tends to go green and rises upwards. This is due to people starting to invest on cheaper altcoins as they think that bitcoin becomes more expensive and can't afford it. The same thing follows when the price of bitcoin falls. Altcoins follow up too and starts to decline as people start to dump altcoins to invest on bitcoin.