If I want to invest my savings on the stock market in companies that are in business in particular technologies that I think will be in demand in the future, how do I find them? For example if I think that eg. hydrogen will be used a lot in future transport, how do I find stocks that are involved in this? Another random example is eg bowling-alleys - how could I find companies involved with bowling alleys for example?
For a macro picture, a screener like FINVIZ might get you in the ballpark. Their data base has 7,500+ stocks and ETFs with the industry and sector. This might be effective for a small category like Industrials/Farm and Heavy Construction Machinery that has 20 or so names but perhaps utterly ineffective for sectors like Finance, Technology, Biotech, etc. Beyond that you'll probably just have to google generically like bowling alley manufacturers, bowling alley installers, etc.