This seems to be an img file. Do we use adb or fastboot from cmd to install this??
You must be rooted to use this method. Download the above file. Using adb shell or terminal emulator:
dd if=/sdcard/recoveryfilename.img of=/dev/block/mmcblk...
try supersu, from my point of view superuser seems to have a few problems with the s4 , atleast this was the case with my phone.
with mirror i meant another host like for example google drive or so. my provider recently started to heavily limit the speed of most och... it would need days to just download the rom.
there also is CatComic which cost money but is worth it.