I could check the market, observe the price and buy and the next minutes, the price might crumble.
No, there is no guarantee that the price may fall. As in the case of bitcoin, for example, when it fell from around $21000 to $15500 three years ago. And, unfortunately, I cannot boast that I am well able to choose cryptocurrencies for investment. Lately, I've just been investing in JLP:
https://www.coingecko.com/en/coins/jupiter-perpetuals-liquidity-provider-tokenInvestors have learned and it is better to stick to Bitcoin and a handful of alternative currencies which are time proven, instead of venturing and gambling their money with shitcoins.
What do you consider to be a time proven alternative currencies? For example, EOS is a time proven or not? It's from 2017 and still alive
https://www.coingecko.com/en/coins/eos