The length of time it takes to download 1 GB of data depends on your internet download speed.
So for example if your download speed is 1 MB then it will take around 2 to 3 minutes to download a 1 GB file.
If your download speed is 10 MB then it may take only around 14 to 15 seconds to download that same amount of data.
The slower your internet download speed the slower the download will take but the faster your download speed the faster the 1 GB of data will download.