It's never the time to short a company, even a really bad one. You have only 100% upside, infinite downside, and you have to time it perfectly. A short can be a part of a combination strategy where you go long on one company and short on a related one, but you still have to be really careful.

If DB stock increases 50% before it crashes, would you be forced to sell at the top and lose all your money?

If you think they are going belly up this year it is far cheaper and safer to buy a put. You risk losing the money you spend for it up front but your losses are capped. Right now the 25 strike for a DB Jan 15 2027 put is 2.50/2.85 bid/ask. DB is sitting at $29.44 as of yesterday's close. That's $285 bucks up front that gets into the money if DB falls beneath 22.15 by Jan 15th 2027. But if it moves down sharply in the near future you could just turn around and sell that put for a profit long before expiration.

This is not financial advice, it is gambling advice.