Using categories and tags for your blog posts will help your Google search placing, as well as making it easier for people to navigate your site.
But it’s easy to get it wrong and end up creating a mess.
The basic rule of thumb should be each post should be in ONE category with multiple tags.
See this article for a guide to using categories and tags effectively: https://www.elegantthemes.com/blog/tips-tricks/best-practices-for-using-categories-and-tags-in-wordpress