Neumann initially studied business but when he was nineteen began an apprenticeship to a book and picture dealer.

[2] In 1910, Neumann returned to Berlin, Germany and in 1911 opened a book and art shop where he exhibited the work of Edvard Munch and others.

[5] He exhibited artists such as Max Beckmann,[6] Conrad Felixmüller, Otto Dix,[7] and Rudolf Schlichter[8] at the very beginning of their careers.

B. Neumann's name became involved in an art restitution lawsuit filed by the heirs to Alfred Flechtheim in 2016.

16-09360, the heirs of Alfred Flechtheim claimed that six works by Beckmann (Duchess of Malvedi (1926), Still Life with Cigar Box (1926), Still Life with Studio Window (1931), Dream—Chinese Fireworks (1927), Champagne Still Life (1929), Quappi in Blue (1926) ); one work by Gris (Cruche et verre sur un table (1916) ); and one work by Klee (Grenzen des Verstandes (1927) should be restituted by the Bavarian State Paintings Collection because of their loss due to the Aryanization by Nazis of Flechtheim's art gallery.