datakick

No difference, it's the same hook. hookDisplayHeader is an alias for hookHeader.  

You can use solution outlined in this stackoverflow answer
To make it work in tb, edit file /js/admin/tinymce.inc.js and paste the code snippet into default_config:

Tracked here: https://github.com/thirtybees/thirtybees/issues/1040

1.1.0 contains some fixes in this area. For example, this one might fix the problem for you. You can either apply this commit manually, or use core updater to upgrade to 1.1.0

@yaniv14 was right, this bug was already fixed in January, but we forgot to release new version. I've just packed and release new version of this module 

you can't download github repository and use it as a module. Github contains source code that needs to be build.

This looks like a bug in thirtybees core, or some override is messing around.
If you send me ftp access, and back office access, I can have a look into this for you.

There is really something very wrong with your site. More precisely, there is some cache somewhere that is returning non-thirtybees files.
1) Thirtybees contains notification.js file, but this file does not contains references to show_new_orders at all
2) thirtybees version of dashgoals.js javascript file contains this content on line 163:
$months = $this->setMonths($year); As you can see, there is no reference to $, so the error can't be trigger.
The only explanation is that something somewhere is returning old/prestashop versions of these files. Please make sure to
1) clear browser cache
2) clear server cache
3) clear any proxy server cache (nginx, cloudflare, or any other service that might be between your server and your browser)
 

When some error occurs, thirtybees tries to log it into file. But in your case, because of incorrect directory permission, it's not able to create file in /usr/share/nginx/html/log/ directory, thus failing with this warning. And we don't know the root cause of this problem, because the original error is lost.
So, first of all, fix the directory permissions so it's writable. Then test again, and let us know what error message appears in the error log.

Sorry, that is not a best solution. It is just a cover-up of a bigger problem: there is something in your system that is trying to set Blowfish object inside your Cookie. There used to be a _cipherTool property inside Cookie class. This protected property used to hold cookie encryptor instance. 
I bet you have some Cookie override that tries to set this (now not existing) property, which in turn causes the fatal error.
You can try this:
revert your fix edit class Cookie.php at the very beginning, add this line: protected $_cipherTool; That should fix your problem. Anyway, this is a core compatibility issue, and it should be handled in the core. 

there shouldn't be any directory classes/range/pdf
I suspect you accidentally copied directory classes/pdf to classes/range/pdf. This can confuse autoloader, because there are now two classes with the same name.
To fix this
1) ensure that directory classes/pdf exists and that it contains file HTMLTemplateDeliverySlip.php
2) delete directory classes/range/pdf
3) delete file cache/class_index.php