I don't know how to explain. But anyone can help me with this? I mean, how can i customize my opencart categories bar so it can display all my categories?
You will need to edit your menu section of your stylesheet.css to make all your top categories fit on the bar. You will probably need to change font size and padding.
Running Opencart v3.0.3.9 with multi-stores and the default template from https://www.labeshops.com which has links to all my stores.