when i would try to search something so that i could know whether someone has already posted it before or when i have a question to ask and i would search it in the search bar, almost all the time nothing would show up. ...
Use google instead together with keywords and "site:bitcointalk.org" it will show topics related to your search only from bitcointalk if there is something related to it. Forum search doesn't work sometimes depends on your search keywords, that's why forum recommends using google search too.
Using a Google search is more effective than searching on forums, Google can display more complex results according to the keywords entered. It is no wonder that members on forums prefer to use Google search rather than forum search because the results displayed are very different. Members on the forum recommend Google search for their own reasons and it doesn't mean that the search engine on the forum doesn't have the ability to return better results, I also often use it when searching for something light, but if I want to see related topics, I will switch there.