I cannot restart the download in the download manager or any other browser as I have already downloaded 9.9 gb

Some websites allow for resuming a download. Others do not.

I would tell you to try Firefox in Safe Mode to see if the problem is still there. But a 15gb file, and 6 hours ! ! !

This download manager works separately from the browser. The browser tells it what to download, and off it goes.

http://www.freedownloadmanager.org It is a powerful modern download accelerator and organizer for Windows and Mac.

I have alredy downloaded 9.9 gb

I do not want to restart the download again in download manager

Please help fast

As I said;

Some websites allow for resuming a download. Others do not.

We can not do the normal checking because of the size of the file and its download time. Try the download manager. You will need to delete the partial file.

Note: Sometimes the manager works faster then Firefox does.

Why do you have written 15 gb for 6 hrs?

That is what the first screenshot shows.