Hey. I have 4mbps plan and it only occurs for some websites if I download something from other website, it downloads at full speed on my handset.
If I use those websites (which are streaming at slow speed on my handset) from my pc then they run at full speed and they also buffer.
That "4mbps" connection is between you and your carrier. From there to the site you're downloading or streaming from is whatever it is at the moment. (And it can vary with the load on some router between you and the server - if there's some fast-breaking news, and one of the routers your connection goes through also handles a lot of traffic to a news site, you'll get a terrible connection until that news becomes yesterday's fish wrapper.)
your PC uses your wifi connection - which I can guarantee doesn't enter the internet at the same place (or use the same path to any given site) as your data connection on your phone, so you're not only comparing apples to oranges, you're comparing apples to elephants. A data connection and a wifi connection can't be compared.
If you could give us a lead to the site that you get the bad connection from, we could try it under various conditions to see what happens.
Also, if you're in the US and using TMobile (I don't know if they play the same trick in other countries), they connect to video streaming sites at high speed, then stream the video at a much slower speed, saving them bandwidth - and giving you problems.
Seeing that the sites buffer even in your PC, though ("buffering" means that you're watching the video faster that it's coming to you over the internet, so the device displays what it has, then waits to get more - just in case you're using the word "buffer" wrong, as a lot of people do), the path from your wifi (for the PC) and from your carrier (for a data connection) to the site is slow. There's nothing anyone can do about that. It's just how the internet works. It was designed to get the data there
eventually, not
immediately. (The original design was for email, and if an email is delayed by 10 minutes, or even by 10 days, it's not that critical. The internet was never designed for videos or immediate chat.)
There
is something you can try, but it's a lot of hassle on your part. Get internet service with another ISP, with a free <some number of days> trial. If that one isn't better, try another one. and so on, until you fiend either that one of them is useful or that none of them can get to the sites you want without delays. (You can't watch videos from a poor or overloaded server halfway around the world without buffering at best and disconnections at worst.)