In 1907 started the building's extension, which was initiated by the First Superintendant Privy Councillor Gerlach. In 1908 already the whole western part of the today's commercial center building was ready built, on the basis of architect plans by Professor Schwechten, the Secret Government Building Officer in Berlin. At first no change happened in the old building part, even though the transfer of the commercial center hall into the western part was already decided in the beginning. Rather the façade of the western part was completed in a great hurry because one didn't want to disturb the impression of this location by a bare brickwork, by the time of the inauguration of the Borussia monument. The new commercial center hall had its grand opening and was placed in service on April 2nd, 1908.

Only after the entire completion of the west wing, the old commercial center hall was equipped with stores, and upstairs converted to flats. The commercial center building has its outer shape of today since 1909.

The Dange bulwark, which the merchant guilde was obliged to maintain, consisted of wood until 1924, and got its current appearance just this year.