Theme development

I'm working on a theme that has a field color_theme which is set by authors on pages. This allows them to group similar pages together within a certain color style - eg. background colors, pullquotes etc.

Within other pages I am using the fantastic paragraphs module to create a page builder of sorts, and one of the fields which is used a lot is a 'button' field, effectively a link.

Within preprocess_field I'd like to set a variable for the twig template based on the logic below:

I'm so frustrated with customizing the look of a Drupal theme I'm thinking of switching to another platform. The problem is seemingly simple: I want to change the styling of a starter theme. The problem is after entering the css to make the type size of an article body larger, no change is seen.  I've tried Stark, which I thought would be an extremely simple way to change the css, but that was not so. Any suggestions on how to find a theme with styling that can easily be changed?

I would to do a simple thing in twig template but it appears to be more complicated than I thought.
So this is what I would to do:

    {% set corps_attribute = create_attribute() %}
    {% set corps_classes = [
    'col-md3 col-lg8 row-md3 row-lg5',
    'type-' ~ node.bundle|clean_class
    ]%}

but this doesn't work:   

    {{ content.body({corps_attributes.addClass(corps_classes)}) }}

and give this error:

Hey Guys,

I installed the Twig Tweak module in order to display a block in my twig template.

I created a View with a contextual filter for Authored by on logged in User IDs.
If a user has ever inserted a review, then it will display the review for that user.

Intended result:

• The if statement checks to see if the body of the block is empty.
• If the body of the block is empty, jump to the else statement.
• If the body has content then display the block

Actual Result:
The block is displayed with or without content.

Hi Community, in the past I used firebug, it was easy to change website and to see where the css file to change is located. Please could you tell me how to use Web inspector (safari). And how to use it. 

Thank You 

Mibadix

I everyone, this is my first message ever in the community, i hoppe it will be a long relationship. 

Im trying to learn to develop personalized modules and controller on DRUPAL 9 with Drupal APis, etc... and i'm trapped for around 1 week now in a probably tiny and idiot problem, but the true is that i don't find the solution. Let's try to explain myself:

1) This is a controller where i just want to list a RSVP List from a query from a database.

2) This part of the code is running ok: 

   \Drupal::messenger()->addMessage(t("@person in the list:",