Magix download servers are notoriously slow, even if you have a fast internet connection, but I have never seen it that slow before. I would expect that traffic is higher at the moment, due to the release of Vegas Movie Studio 14.
One thing you could try is to re-boot your Modem/Router and get a fresh connection. Also re-boot your computer and begin the download again. Sometimes doing this can improve download speed.
FYI: My experience with the download manager (DLM): started at 520 KB/s...and eroded to <400KB/s. From Microsoft, Apple, Google I can get full 120 Mb/s. It is strange that the Magix download server hasn't utilized Amazon or Azure, etc. Set your expectations low.