The oldest attestation of a Germanic language is the Wulfila Bible, written in Gothic language. Unlike English, Dutch and German (West Germanic), and Icelandic, Norwegian, Swedish and Danish (North Germanic), Gothic belongs to the East Germanic subbranch. All East Germanic languages are extinct.
The Gothic language was (much) more inflecting than modern Germanic languages: it featured at least 4 cases (nominative, genitive, dative and accusative) and possibly a 5th one (instrumental). As Latin and Greek (but unlike most modern Germanic and Romance languages) Gothic had a synthetic passive voice and verbs were conjugated in indicative, subjunctive and even optative (as Old Greek).
Besides Gothic, the East Germanic subbranch contained other Germanic languages - Vandal, Burgundic… - of which there are no attestations.
Till the 18th century, a Gothic dialect used to be spoken on the Crimea: the so-called Crimean Gothic. However, linguistically Crimean Gothic shares a lot with West Germanic (particulary with Low German), and some linguists consider Crimean Gothic a West Germanic languages with some older Gothic (East Germanic) influences. Today, Crimean Gothic is completely extinct as well.
