How to management layout-grid : (CSS) [Issue]

Hello I apologize I believe I found very similar questions however in none of them got an expected answer.
First of all I have consulted all the basic documentation regarding layout and some links * that I believe are very good as below.
However I did not understand how the division of grids and containers within the plotly works - I am not a professional programmer just a hobbyist - I managed to solve my problem with the bootstrap module of our documentation however I am wondering how I use the combination of Divs and CSS using the IDs. of class for the example below.

Links:

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Nothing until now… :frowning: