For me the links except #21 are working and the cbr files can be opened.
Have you tried downloading them a second time or renaming the cbr-files to .rar and opening them with WinRar? If WinRar shows you crc errors, then this might be caused by your firewall (though it's a rare problem with downloads, it's much more common with uploads).
If WinRar can open the files, try to extract them all to a folder and then repack this folder into a zip or rar archive. Then you can change the extention to .cbz (for zip files) or .cbr (for rar files) and your reader should be able to open it (provided the extracted pictures were not damaged).
Complete issues translated into German: 13-29 (including '97 and '98 Special)
Bonus stories translated into English: #13, 14, 15, 18, 19, 20, 21, 22, 23, 24, 26, 27, 29, 30