It is important to find the right keywords or search terms for your search. Which words you choose decides what result you will get. One tip is to start by finding the relevant key words in your research question. Here is a video from University of Houston Libraries with tips on how you can think when choosing your key words.
Key words can also be combined in different ways in order to get more relevant search results. The most common way to do this is by using so called Boolean search. You can learn how to do a Boolean search in this video from John M. Pfau Library (California State University).