$NVDA.US$ hi imna completely new stock buyer/ trader and i w...

hi imna completely new stock buyer/ trader and i would love quick advises.

is it a good time to buy stocks e.g nvida, futu, tesla now especiallt when its having a downwards trend? ive heard the secret to profitting from trading is to buy low and sell higher, which means i can sell at a later time when e.g these stocks i mentioned above become green again?

and usually, how low (e.g how many percent) should it go before its an ideal time to buy? like e.g now tesla is only -5%, the drop is too low?

also, how are moomoo fx rates (since i believe there, what are the exchange service fees each time and what are all other fees that comes with trading? pls advise

which platform is best to buy stocks to incur the least fees/chsrges and to lose the less sst money to the exchanging of currency in the long run (e.g moomoo, ibkr, webull, SYFE, or any recommendations?

cheers