Hi,
My name is Budhi Hamdani and I am a professional system administrator. Regarding with your issue slow at download and when you're backup not finsihed, the reason behind of that could be many reason some of them regarding your resource issue (cpu, memory), bandwidth issue (how many bandwidth your vps has?) , query database issue etc.
I could troubleshoot and fix the problem if you need to, and i am gonna give you some documentation so next time you found the same problem you could check it for yourself. Looking forward to hearing from you.
Best Regards,
Budhi Hamdani