Google will only take you so far... in particular it can't show you areas of the web which aren't freely available, including the many specialist resources purchased by the library.  Subject portals contain links to all sorts of relevant online resources, and they have usually been checked to make sure they are trustworthy (however you should always do your own checks).  Here are some subject portals for German studies:

We subscribe to many resources relevant to German Language and Literature.  Some highlights are shown below:

Many quality databases and resources are free at the point of use.   Examples include:

You may find the following mailing lists helpful:

As well as the resources mentioned above there are some other useful links that may be of help to you throughout your time at Oxford