I tried many times to download stuffs but download speed is just 8kb/s 6kb/s or sometimes 12kb/s

....i think you are using AIRTEL network connection.
In india fastest 2G connection is provided by IDEA network about 30kb/s next was VIDEOCON network 20KB/S.....I am a IDEA user & no problem with downloading about 400mb file(3hours) also.so if you use fastest network than no problem during the download
(sorry for bad english)