This could be due to to numerous factors:
- Upload speed is slow: To test your upload speed, please go to: www.speedtest.net/mobile/
- Your WiFi is set to turn off during sleep: To change this setting, please refer to the following article: http://help.mightytext.net/knowledgebase/articles/49300-set-wi-fi-sleep-policy-to-never-
- Too much internet activity: Try to run backups when there is minimal internet activity, it is recommended to keep the first backup to run overnight and plugged in.
- Some ads blocking apps might slow down G Cloud and affect the upload process, so try to disable them temporarily to see if this speed up the upload.