{% if content.field_inner_hero %}
<div id="innerhero">
  {{ content.field_inner_hero }}
</div>
{% endif %}

Better

{% if content.field_inner_hero[0] %}
<div id="innerhero">
  {{ content.field_inner_hero }}
</div>
{% endif %}

{{ title_prefix }}
{% if title %}
  <h1{{ title_attributes.addClass('title').setAttribute('id', 'page-title') }}>{{ title }}</h1>
{% endif %}
{{ title_suffix }}

Another way

<div id="nodebody{{ node.id }}" {{ content_attributes.addClass('nodearticle') }}>

I realise the following is not very helpful as I've pasted my code solution and didn't have the time to explain it.... Now I'm looking at it wondering what I was trying to solve. Anyway, if I remember I'll come back and fill in the blanks...

https://www.mediacurrent.com/blog/simplify-menu-and-twig-macros/

menu--main.html.twig

I had some issues installing PHP 7.3 on Centos 7 With Yum. I found the solution here: https://unix.stackexchange.com/questions/435242/problems-installing-php-7-on-centos-7-with-yum.

This is such a vital part of the build process for D8/9 that it's a shame it's not something you just tick in the CMS. Then again, I believe the idea is to have the additional settings/files on your local machine and not on your production server. That way the production server is always fully cached and your development environment always has caching turned off. Which does make a lot of sense.

In Drupal 8/9 you create a MYTHEME.info.yml file to specify the theme name, and base themes (if this is a child theme), regions, etc. One of the items is a reference to your 'libraries'.