Death records for the years 1874-1920 are available on Ancestry.com.
Death indexes for Berlin Civil registration records can be accessed at http://landesarchiv-berlin.de/. Click "Online Recherche" then click on "Namensverzeichnisse". You will need to enter the name of the Standesamt to retrieve the indexes. These indexes go beyond those available on Ancestry.com. They are arranged by year and grouped under the letters of the alphabet. A certificate number is given and the death date is given in some of the indexes. Some of the actual records may have been destroyed. The files are large and take some time to download. No images are available.
Another explanation of the indexes can be found here: http://www.content.landesarchiv-berlin.de/labsa/show/help.php