Theme development

page.html.twig is creating eternal header wrappers, instead of full Page Wrapper;

and I am unable to accomplish a Full Page Wrapper.....

I have checked my DIV's, but Drupal is Adding some extra DIV in most illogical place each time... I am refurbishing a Bartik duplicate's page.html.twig

It is also proved - because I can accomplish a Primary Menu - to Footer full menu wrap; but not to include Header, Secondary Menu...

OK, full code is something like:

So, I am creating my first Druupal 8 Theme..... On Bartiks base, but changing all css & page.html.twig

I was editing page.html.twig of course....

and it seems, I can not make all Region Div's in vertical line, as soon I look into Firebug - some Mystical Div dialog-off-canvas-main-canvas shows up and cuts off all Header and Secondary Menu divs from the rest flow of the page.....

my page.html.twig looks like:

I'm new to Drupal, however I've designed other sites in the past using various applications. I've been poking around and learning what Drupal 8 has to offer and trying to use just Drupal 8 and a text editor. From what I have discovered there are several things that are not accessible to edit from the Drupal 8 "toolkit".

i have created a module.
in my module i have created a form. Form submits data successfully in database.
i am getting data from database in a controller file. till that point everything is working fine.
Now i want to display data in my twig file.
How it is possible to display data from database in a twig file.?

What theme do you recommend for creating sub-theme (I prefer simple css or less)? Im not very experienced, I know css, less, html, basic js. I use grunt. I'm using bootstrap at the moment but don't use its functionalities so there is no point using BS and it has a lot of code that makes my work complicated. I want to make simple website, gallery, info, contact, news etc. If possible i'm looking for a responsive theme that won't be deprecated in future Drupal versions.

I'm not getting how to create a sub-theme. I am just hacking Bartik. But I was trying to do it in a child theme. All I want is to add one style.css file so I can make some overrides to the default Bartik theme. Here is my info and libraries file.  I have my style.css saved in the same theme folder as the info and libraries files. 

Thanks for any help. It seems right, but I can't get it to load.