HTML Site Template hard rejected

My html template was hard rejected a few days back. Can anyone please help me identify what i can improve about my html template to get it approved?

I received the following email:

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Here is the Demo Link: http://www.d5bd.net

Hello Sir,

First you need to learn UI design.

Don’t worry, there are many free resources and courses that will take you to the next level.

My advice to you and the shortcomings in your theme:

White space:

White space is very important.

You should use fill, margin, alignment elements, typography, beautiful shadows

Use font sizes and titles by typography.

Use beautiful gray.
exp. hex code # f1f2f6 …

Use capitalized texts and strong keywords etc.
I’ll try to help you if you have any other questions.