Menu design is only visible while using the WP customizer

I apologize for posting my question in English. Unfortunately, I do not have an Hebrew keyboard (but I can perfectly read and understand the language).

The issue that I am experiencing is that the website menu is only showing its nice design when I am using the WP customizer. Once I finish the customization the design in completely different and bland.

Here are the pictures that show the issue:
How the menu looks while working with the WP customizer:
How the menu looks without the WP customizer:

It works perfectly while developing on my local machine but not on the host's server.