Most of the time, the slow download is caused by the following reasons :
1.The network is not stable .
2.The third-party where the resource is stored is not stable.
3. BitTorrent download is slower.
You can try the following operation :
1.If the video is from YouTube, you can try to open YouTube in the system browser ,play any video and check whether it can be played fluently or not. If the video can be played fluently, it means that the current network is stable.
2.If the download video is from Movies, Music or other channels, you can try to download any video of YouTube and see the download speed is normal or not. If the download speed of YouTube is normal, it means that the slowness of the current download task is caused by instability of the resources .We suggest you wait patiently or try again later.