> If I buy a stock that is now 16$ but was 26$ a few days ago, will it go back to that price and i can make a small profit ?
Most people think probably, since the stock markets have always recovered after previous crises. But it might potentially take weeks, months, or years (if the impact of the pandemic and other troubles causes an ongoing weakness in the economy). There's also a risk that particular companies or industries will be so severely affected that they never fully recover; for example, individual companies could go bankrupt or could be acquired at a lower valuation than their peak value.
Here in California, which currently has a less disruptive COVID-19 outbreak (and less disruptive responses to it) than much of Europe, there have already been reports of some small businesses failing. Someone who invested in those businesses on the assumption they would later recover could have lost the whole investment. Larger businesses can fail, too, though usually on a longer time scale. For example, it's possible that some travel-related companies that are especially impacted by reduced travel will have to sell off their assets and operations to other companies, maybe at a comparatively low value.
The point of this is that, in general, stock markets as a whole, and economic sectors as a whole, have always recovered from crises and disasters -- potentially providing profit on some timescale to people who invested during a crash -- but that this may sometimes take a very long time¹ and is definitely not guaranteed for any individual company. Therefore there is never an opportunity to invest in stocks with absolutely no risk, although a financial advisor may be able to help you estimate and manage your risk.
Even if a particular community is convinced that a certain stock or the market as a whole will probably move in a certain direction, it's never a guarantee. Your gamble may have a positive expected value, but that doesn't disqualify it from being a gamble.
¹ If you get really unlucky, there could be other economic disruptions that interrupt the recovery (other disease outbreaks, natural disasters, political instability, wars, effects of climate change?) and so the economy may not recover on the timescale that you expected it would.