Custom article page formatting

I’m trying to create a custom article page. Suddenly I’m unable to assign page width to the text in css. I can’t understand what’s going on.

I’ve created a data file (hugo new articles/article1.md) and an article1.html partial. It picks up the header and footer from the page template.
Partial:

{{ partial "global-header.html" . }}
{{ $data := index .Site.Data .Site.Language.Lang }}
{{ "<!-- Start linuxguide Section -->" | safeHTML }}
<section id="linuxguide">
  <div class="container">
	<div class="row">
	<div class="column">
      <div class="block">
         <h1>{{ .Params.title }}</h1> <<<=== this is not rendered
         <hr />                                    <<<=== this is not rendered
         <div class="col-md-4">
		      {{ .Content }}            <<<=== this is rendered, but page width is not applied
	</div>    
	    </div> 
    </div>  
    </div> 
  </div>
</section>
{{ "<!-- End linuxguide section -->" | safeHTML }}

In .md file there is a

# Header               <<<=== this is rendered, but page width is not applied, starts from the screen border
Some text              <<<=== this is rendered, but page width is not applied, starts from the screen border

Actual rendered html:

<main>
<h1 id="why-linux">My Heading</h1>
<p>This is my text. Why is this happening???</p>

<table class="table table-dark table-bordered">
... Table looks fine. ...
</table>

you have to set some frontmatter in your .md file

Dear @ju52, thanks a million! You are 100% right! Being overwhelmed with info, I missed the id in the front matter! The filename was the same as that of html - and I missed the main point! So, the unambiguous relation between the .md and .html is exstablished by the id in .md!