I lost a big sum of money because of bitcoin fall. What can I invest in to avoid risks like that? Or at least to bear lower risks?
In crypto universe there isn't any way to avoid risks like this or to bear lower risks. When investing in crypto currency you have to take all the risks and accept the consequences.
As this market is very volatile, you should never invest thinking in short run profits, because sometimes it will take months or years until you are able to cash-out profits. I see you started your investment very well, because you picked the right coin (bitcoin). You just need to be more patient and don't desperate yourself after a fall in price next time. Buy bitcoin again and keep holding.
Remember many people bought bitcoin for 19,000$ years ago and had to hold it for few years until they could sell it for 64,000$ this year, during the last ATH.
Conclusion: the profit isn't overnight like some people say on the internet.