How do I use contextual filters and relationships to show related articles?
I have implemented the same in one project in Drupal 7 to display products of same catalog.

You can create a views of article content and can create a contextual filters for tags. It will display all the article of that tags. 

You can follow below step:


Add a contextual filter of tags. Checked radio button "Provide default
value". 
Select "Taxonomy term Id from url" in the type drop down.
Checked "Load default filter from node page" check box. 
Checked "Limit terms by vocabulary" check box.
In the Vocabularies section, checked the check box of Vocabularies
(tags) which you want to add filter in the views. 
Under the more section, checked "Allow multiple values" check box, so
multiple tags can use filter the term.


You can find below image for reference.

You also need to add contextual filter of node id and follow below step, so current node page will not display in related views section.


Add content: Nid contextual filter in the views.
Checked "Provide default value" radio button and select "Content id
from url" in the type drop down.
Under the more section in contextual filter, checked "Exclude" check
box.