If you are having trouble uploading large videos, you can use Handbrake (free tool) to reduce them.
After downloading the application, follow these steps:
Add the video as a source
Select a folder as the output folder
Use format = mp4
Encoder = h.264
Now, you should pick a video quality. We recommend using HQ720p for very HD quality and HQ 576 for reduced video size.
After you finish setting, just click on Start.