Why i can't create section by <div class="section">... </div>

did you add any CSS for that? Let us see the code you tried for better understanding of your question.

Do i have to

You can't have a div with a class name of section because there is already a tag for <section> See https://www.w3schools.com/tags/tag_section.asp If you want to create a section use the <section> tag.

Thanks for helping