No one can be 100% sure here. Even if you have a thorough analysis, the accuracy is only 90%. However, you can find a reasonable starting point and ending point for profit.
Yes no one is certain in bitcoin that our investment is safe. Just make sure that we invest on our willing money to invest only. Even their is hackers keep safe your btc in a wallet that is secured.
Unfortunately there is tons of misinformation and manipulation regarding Bitcoin's price and cryptocurrency in general. In order to understand why BTC might go up or down you must first understand how the fiat markets work.