Ok, backing up actually works, but that's it. You better NEVER have to restore anything.
After a HD crash I had to restore several TB of data. This is not possible at once, you have to split up the data to actually be possible to download anything.
Downloading with a browser is WAY too slow, downloading of one chunk of 300 GB lasts for 2 days, which sucks because of the forced connection restart of internet providers here, so downloading is so slow that it is actually not possible with the browser.
Ok, there is "Backblaze downloader" which should be able to reconnect and resume downloading. The problem is, this app does not even start to do anything. Starting to download? Nah, not with this app.
So actually you pay for backing up your files but you will not be possible to re-download and restore them if it is more than some GB.
Backblaze is a joke. NOT RECOMMENDED!