At the moment there are problems when you try to get access from outside the University network (Technische Hochschule works) on e-books and e-journals from Elsevier. The simple login by SSL-gate (the webportal) does not work at the moment.
Nevertheless you can get access by using the Pulse-Secure VPN provided by the ITSC. You can download the software here (Windows and MacOS):
Here is a short introductions to install it (Windows and MacOS):
After installing and starting the software make a new profil and insert the Server-URL sslgate.uni-luebeck.de as default connection. You can choose a name for this profile and then you have to save the configuration. After that you can use the app and make a VPN-connection by pressing Verbinden. You will be asked for zur IDM-dates, they are the same as those you use for moodle and so on. Please do not save this dates for security reasons, espacially on mobile device this can be a security leak.
On this page you find the German introductions and how to install the VPN-software when you are using Linux: (German)