Its been 5 months now, since I joined cryptocurrency ,I've seen many ups and downs in Bitcoin Currency and Altcoins even in those Rank 2 to 100 in Coinmarketcap, but I just want to clarify why every end of the year starts in September then up to December Bitcoin fly high, any fundamental reason why does the value of Bitcoin and other currency go up?
I wish that would happen all end of the years, so all crypto lovers would be rich one day

There is no such situation, different scenarios occur every year. There's no such thing as easy money.
last year prices did not rise at the end of the year. even more likely to decrease? you are right. not every year prices will rise at the
end of the year. of course changes in price will depend on certain conditions