Hallo Mihai,
What are you actually looking for? If you are searching for Eastern Front material, from what I have seen you will not find very much after May 1945. It seems that most of the decoding effort was concentrated on the Western Front from then on.
A good way to approach HW 5 is to read through the DEFE Main Series for the same range of dates (see here for the file references:
http://www.ghostbombers.com/Ultra/defe3list.html). All of those files can be viewed online or downloaded free and at the top left of each message (see attachment) is a CX/MSS/ serial number. That number is the correspponding message in an HW 5 file. The National Archives catalogue will show you which files each one is on.
(Each HW 5 file is maybe 250–300 pages, by the way).