Theme development

I have a field collection (field_facebook) that has two items:
* An Image (field_img_dflt)
* And a Link (field_fcb_link)

I want to theme these item in my twig file, so i did the following:

I have a website with a previously purchased drupal theme, but it is no longer available and I can not claim further service on it. Prior to all previous updates, it worked properly. Now since the last two updates of drupal commons, the module is no longer working well.
As soon as I launch the theme, comments are no longer visible. They are therefore present, are created and are visible in other (standard) themes.
This applies to logged in users as well as anonymous users. I also checked the access rights for this. I'll just get the "Add Comment" button.

Help! I have inherited a Drupal 7 site that uses Glyph Icons for Facebook and LinkedIn and the user wants a YouTube icon added.

I have never heard of glyph icons before starting this and still am not sure how they are implemented.

Like I said, it is a Drupal 7 site and the theme is based on Bootstrap.

In the theme's /css/main.css file I found reference for Facebook:

Hey there,

I want to show on each page a different image in my header. How can I do that?

I already found several solutions, but nothing that worked for me. I want them to be in an independent region (ideally in the header under the navigation, outside of content).

It's driving me crazy. I've worked with a lot of other systems than Drupal before but cant find a good solution...

Hey there,

I'm new to Drupal and I don't understand how I can find a modul's template.
f.e. if I want to edit html/php etc in the navigation, where do I find the template for it?
I'm really having issues with that, because I need to edit a lot of templates, but I can't find them.. some are in my theme's folder, others in the core folder...

Does anybody of you can give me an advice? How are you handling with that?

thanks alooot!

G'day, fellas! This is my first experience with drupal and I want to explore more into it.
I am trying to take advantage of alvarotrigo's js plugin fullpage which allows to place beauts parallaxes and sliders in a very simple way.
As expected, my first impression of drupal was everything but simple.