It is common to modify your topic during the research process.
You can never be sure of what you may find. You may find too much and need to narrow your focus, or too little and need to broaden your focus. This is a normal part of the research process. When researching, you may not wish to change your topic, but you may decide that some other aspect of the topic is more interesting or manageable.
Keep in mind the assigned length of the research paper, project, or other research assignment.
Be aware of the depth of coverage needed and the due date. These important factors may help you decide how much and when you will modify your topic.