Here you can find helpful websites (mostly in German):
Maths:
Serlo - "Mathe für Nicht-Freaks" is a compilation on Wikibooks in which the vast majority of topics from Analysis and LADS are explained in detail, described and illustrated. Anyone who is struggling to understand the lecture content in these subjects is sure to find what they’re looking for here.
wolframalpha.com is not only a highly powerful calculator, but also helps with systems of equations, plots graphs and calculates how many kilocalories there are in one cubic light-year of ice cream
integralrechner.de is the integral calculator with calculation path
Informatics:
learnxinyminutes.com provides an overview of the syntax of all modern (programming) languages and file formats
University internal:
univis.uni-luebeck.de lists all events, rooms and people at the unversity of Lübeck
qis.uni-luebeck.de provides access to your marks and exam registrations
https://uzl.hispro.de provides access to your address information, study documents and more
moodle.uni-luebeck.de is the learning and organisation platform of the university
https://www.itsc.uni-luebeck.de/dienstleistungen/it-infrastruktur/fernzugang-vpn/cisco-secure-client.html sends you to the installation of the university's vpn, using which you can surf on the university's network from the outside.
zhb.uni-luebeck.de ist the website of the library. You can search, lend or extend books here.
Other:
detexify.kirelabs.org finds the commands for Latex-symbols you are looking for
springer.com provides access to many books and papers if you are using the university network