Adding Categories navigation to show certain entries I'm abit lost as to how to structure my FAQ page.
I have a single FAQ page that pulls in every FAQ post, these posts come from the FAQ Entries channel.
But
On the single FAQ page, how do I add a navigation that only shows certain FAQ Entries using categories?
If I understand properly, you want to show related FAQ based on categories.
On your entry template, you could do something like this:
{# Fetch the categories of the current entry #}
{% set entryCategories = entry.yourCategoriesFieldHandle.all() %}

{# Find related entries #}
{% set relatedFaqs = craft.entries()
    .section('faqs')
    .relatedTo(entryCategories)
    .all() %}

{# Display related FAQs #}
&lt;ul&gt;
{% for entry in relatedFaqs %}
    &lt;li&gt;&lt;a href=&quot;{{ entry.url }}&quot;&gt;{{ entry.title }}&lt;/a&gt;&lt;/li&gt;   
{% endfor %}
&lt;/ul&gt;


Change yourCategoriesFieldHandle to what your field handle is and .section('faqs') to the correct section handle for your FAQ's section.