What are the aspects of a good user interface?

I am new to frontend development environments, apart from high responsivity and clarity of user interface,

1. what other aspects do I need to consider to have a good user interface?

2. Here is what currently we are doing with colleagues, link to demo page

from the above demo page assume it's your website, what will you change - from UI and js(interaction) point of view?

Any suggestion will be appreciated.