Complex sentence: The museum shows both international and Norwegian art. The museum also houses three main art collections, donated to the Oslo municipality (and the former Aker municipality) by Rolf E. Stenersen, Amaldus Nielsen's heirs, and Ludvig O. Ravensberg.
Split into simpler sentences: The museum shows both international and Norwegian art. The museum also houses three main art collections, given to the Oslo municipality (and the former Aker municipality). These collections well dontated by Rolf E. Stenersen, Amaldus Nielsen's heirs, and Ludvig O. Ravensberg.