Theme development

I have a D8 site with a theme based on Bootstrap.
I'm using Superfish for the main menu, and all is well - except that the little arrow indicator triangles that show that an item has a submenu aren't showing - but this only happens in Chrome.
They work fine in Safari and Firefox.
The triangles are implemented in an :after pseudo-selector like so:

Hello
Can someone help me about instaling demo theme onepage for d8, by weebpal.
always geting messages with error or blank screen.
Please help me about instalation, using drupal 8.1.8 , I doing something wrong but dont know what.
Please help.

Thanks forward

Hi everyone,

Drupal newbie here.

I've started building a site in Drupal 8 and need some help with an issue I'm having. My twig templates are appear to be permanently cached!

I've installed Drupal 8.1 via composer (https://github.com/drupal-composer/drupal-project) and have plans to run everything through a Docker container. My environment is initialised via docker-compose, which has the following setup:

In most of the Drupal themes I find the IDs #page and #page-wrapper, but it is not available in the Drupal Bootstrap theme.

I tried to find in theme, but maximum I could find is class .container but is covers only that particulate section i.e. header, main-content, footer.

Is there any ID or class in Bootstrap theme which covers entire webpage like #page does in almost all other themes OR if there is not how can I add that?

For styling the theme and applying CSS, I need the #page and #page-wrapper which we can find in most of otehr themes.

Receiving the following error in logs:

Notice: Undefined offset: 2 in my_custom_theme_preprocess_page() (line 157 of /home/sonsoutr/public_html/themes/my_custom_theme/my_custom_theme.theme).

Trying to trace error to no avail so far. Below is the snippet of code referenced above. Any help would be greatly appreciated. Line 157 referenced above is bolded below in the code snippet.

Line 157 referenced above and below:

Hi !

I'm start with Drupal (8.x) and I want to personalise a view by the "rewrite resultat" option.
I try this code