Hermanter

@Hermanter
Sorry that I've been away for a few days, very busy. I am still trying to find a solution to the problem, what I've done so far is that I've downloaded the Office 2019 Volume Edition and I am trying to create a repack of it which will install without problems and can be activated using a volume key. 
Usually, if you want to use a volume key, you would need a KMS server and I guess you don't have one... Very tedious. 
P.S Add this line to your to your script: 
<Property Name="AUTOACTIVATE" Value="1" /> and give it a try.
@Peter Frommann
Sure, if you don't want to install Access, Publisher and Groove, why don't you try this:
<Configuration> <Add OfficeClientEdition="32" DownloadPath ="https://officecdn.microsoft.com/pr/492350f6-3a01-4f97-b9c0-c7c6ddf67d60"> <Product ID="ProPlusRetail"> <Language ID="de-de" /> <ExcludeApp ID="Access" /> <ExcludeApp ID="Groove" /> <ExcludeApp ID="Publisher" /> </Product> </Add> </Configuration> Regards,
SnowBall

Hi, have you uninstall Office 2019? What is the edition of Office you want to install (ProPlus, HomeStudent, HomeBusiness, Office365, Pro or single apps), in other words, which edition is your key for? Please tell me (Very important) Make sure you uninstall Office completely, restart your computer and try again.
Regards,
SnowBall

Actually, do you have other versions of Office installed? if you do, they might be the cause of the problem.

Download this file: https://mega.nz/#!RNFkCaCK!OQOyA635d9nXjjv8kGFTEz6aTrdVA4RzRXkfFt0-M6w and put in in the same folder as your setup.exe and configuration-Office2019Enterprise.xml, run the file as administrator and the setup will start.
Hopefully it will work, any problems, reply below.
Regards,
SnowBall

Humm... thanks for the new link. From the screenshot, you will be installing a 64 bit version which is not recommended by Microsoft as it will cause problems with plugins, please consider change it to 32 bit even your are on 64 bit OS.
The code:
setup.exe /configure configuration-Office2019Enterprise.xml You need a bit of flexibility here, anyway it should work. Just want to make sure that you have the right edition, which edition did you buy? If it is not Pro Plus, comment below and I will get you a new code, if it is Pro Plus, then you are all good.
Regards,
SnowBall

WindowsTH-RSAT_WS_1803-x64.msu, the 1803 is your build number and x64 is the bitness of Windows.
Regards,
SnowBall

Here's some background knowledge:
Each edition of Microsoft Office comes in two (or actually three) different licensing flavours: Retail/OEM and Volume License (VL).
VL licenses are for large companies and enterprises, but in the EU it is legal to sell, buy and use second hand VL licenses (although I do wonder where a second hand Office 2019 key should come from just a couple of weeks after the initial release...)
Since activation for the two licensing models works fundamentally different, MS distributes two different installation files. You can't use a Retail or OEM key to activate a VL installation, and you can't use a VL key to unlock a Retail/OEM installation.
MS only makes Retail/OEM installation images publicly available - no luck for VL users here. Installation media for VL licenses would have been given to the business that initially purchased it.
Office 2019 is also not yet available on MSDN (very strangely), therefore I can't find out the hash (checksum), which would make finding a genuine file quite easy.
Bottom line: there's not much I can do to help you. Better ask the seller for the installer.
(Reminder to all: it's not allowed to post copyrighted files or links to them here, just in case someone knows where to find it. Of course we respect users' privacy and don't monitor private messages.)

@Hermanter, are you blind?
Just kidding, the Volume License Pack will work!
Regards,
SnowBall