My problem is easy. We do not play in English. So all the neat stuff where people are talking, such as the “Welcome” in the store etc. are of no use to me.
My suggestion:
Either have someone make appropriate recordings and implement them, including a button to select the language to be used. (Sindarin, Klingon, German, French etc.)
OR and I think that would be better, make a way for DMs to make their own and import those. Might be nice to offer a database online…
The Syrinscape Creator does allow for DMs to make and import their own sounds, should they so choose! 
Great! Could you please give me a hint where to find a how to?
You need to have the SuperSyrin Subscription to have the Creator.
And then follow the videos here for a how-to!: https://www.youtube.com/watch?v=iBJdKt7RgPU&list=PLFxKCQySfglyTEaK-gSJyHRqhSYLFzq_w
Yes like @HECook said, with the Creator, you can add in your own voices and even share those soundsets as Community Content so that other Supersyrin Subscribers can hear your lovely voice and enjoy the soundsets.
This is one of the reasons why we built the Creator, it allows the community to tailor the soundsets to their needs. The German version of the “Goblin Song” was done this way