Based on a collection of written narratives gathered in the context of a broader longitudinal investigation of the bilingual acquisition of German Sign Language (DGS) and written German by bilingually educated deaf students, the study presented here explores the main milestones in the development of German in order to (a) identify the commonalities and differences between the deaf students’ and other learners’ development of German, and (b) determine the range of intra-individual variation (including language contact phenomena) and its relation to reorganisation phases in the learner grammars. The analysis of the data reveals the structure-building processes underlying the students’ development of German sentence structure. Further, it is shown that the deviances in the written productions pattern with the errors produced by learners of German in other acquisition situations, which provides additional support for the assumption that deaf learners’ acquisition of written German as an L2 is bound, too, to underlying language specific learning processes. Regarding language contact phenomena, the lexical and structural borrowings identified occur at specific developmental phases whereby structural borrowings decrease as learners progress in their development of the L2.