Drupal 8.x

Hi I am new to forums and drupal. I have searched google and as much of drupal as I can but I am at a loss for a solution to a problem that I have just noticed.

I have installed two sites (Main and subdomain) with drupal 8.2 and it has worked great. Somewhere around the 8.2.4 I noticed that if I used the internal contact form for members I got a 500 error. I am not sure when it started.

Is it possible to declare a twig function in a custom theme? This documentation page says you can do it in a module, but doesn't specify if it's possible in theme.

For more context, I'm trying to add a font-awesome icon in a menu link. I have a custom twig template ready for this menu, but {{ link(item.title, item.url) }} always escapes font-awesome markup.

Products and summary Product Kit are in place but when an order is placed and paid for the link to download any file never populates.

Not sure what setup needs to be performed to allow the link to populate or trigger to populate.

When I create my new Drupal site on my localhost, I have my admin toolbar for maybe a day. The next time I fire it up locally, the admin toolbar is gone and I can't manage my site at all.

Any ideas on why this is happening? Also, how can I attach screenshots of my issue?

My university offer their server where we can put things online using our own domain (cs1.ucc.ie/~(studentid)) It has the folder public_html but how do I install Drupal on it?
Sorry if the question is fairly basic.
Would appreciate a response!
Thanks.

I have an entity defined. And on the BaseFieldDefinition I'm trying to set the height of the textarea by rows. But I can't seem to get that to work. Am I going about that the wrong way?