Chrome browser in Android always renames downloaded file to Download.bin
It's possible there may be a problem with the site itself, or the browser. What you can do is to rename the .bin file to the expected filename. e.g. If you downloaded music.mp3 and the browser renamed it to anotherfilename.bin, just rename it to music.mp3 using a file manager.

You could also try other browsers. Give Dolphin, Boat Browser, or Opera a try and see if you still encounter the same problem.