Do you get the same issue if you paste the original code into the Code tab, instead of inserting it as a template?

Is this all the code in the template file, or is there more?

<!-- tekst en of afbeelding in linkel kolom -->
</div>
</div>
</div>
<div class-"container">
<div class="row">
<div class="col-md-3">
<p><img src="https://www.joomlacontenteditor.net/images/Ontvangers/Veronica_Caroline._City_Noordzee_en_Radio_London.webp" alt="Veronica Caroline. City Noordzee en Radio London" width="547" height="369" style="margin: 5px auto; display: block;"></p> </div>
</div>
<div class="col-md-7"><!-- einde kolom -->

All content inserted with template items is processed through the editor, so your invalid or incomplete HTML - it has multiple closing </div> tags without corresponding opening tag - will be "fixed", resulting in:

<p><!-- tekst en of afbeelding in linkel kolom --></p>
<div class="container">
	<div class="row">
		<div class="col-md-3">
			<p><img src="https://www.joomlacontenteditor.net/images/Ontvangers/Veronica_Caroline._City_Noordzee_en_Radio_London.webp" alt="Veronica Caroline. City Noordzee en Radio London" width="547" height="369" style="margin: 5px auto; display: block;" /></p>
		</div>
	</div>
	<div class="col-md-7"><!-- einde kolom --></div>
</div>

This is normal expected behaviour.

The code where it is inserted has corresponding opening tags. So the editor is correcting wrong

But the code you are inserting is processed before it is inserted into the editor, so this code itself must be valid, or it will be corrected.