When you decide to buy and sell should entirely depend on the investor's opinion and analysis, if you don't trust that bitcoin is going to exceed the current value of aound $4,000 and continue rising, either on long or short term, it's better not to invest and risk regretting your decision to invest money into bitcoin at this time, Of course, the price can continue rising, but I believe the decision should be entirely based on your opinion, not external factors.
Of course the choice of investing into something even Bitcoin is his own decision. Whether or not the OP knows how to trade Bitcoins and invest in Bitcoins is a whole different thing. People can put money into something and call it an investment though when they cash their money out and complain that they lost money on that investment it's probably because they got out at the wrong time.
Investing in Bitcoin should be used with a basic understanding of how to invest in things. It's better to purchase Bitcoin and forget about it for a while because the price is increasing.