Thanks everyone for the replies and feedback's. Yup I'm also aware of signal interference/wifi congestion and antenna issues. I think I have tried what I can to reduce the signal interference. Hence, I come down to wifi router not good enough for my use on 30mbps. hehe. 
Had a family member also same issue as mine.

Thanks for the suggestion. Will look into it. (though a bit more on the price for me.  )
And yeah, mine was just upgraded to 10mbps upload to recently. The picture was taken earlier than that.
Now the download is still not ... errrr ...  hehe. 
Thanks for the suggestion. Will look into it.
Thanks.
I'm using using Channel 6, 20/40MHz bandwidth on Wifi 802.1b/g/n (auto).
Not so many wifi signal at my place. Even during no other wifi around, the speed is like this too.
All my devices/smartphones are at least Wifi N, except one Note5 which is Wifi AC supported.
All 6 devices connected to wifi at all times. But only one or two is streaming youtube and doing some light surfing. The rest is just idle/connected.