I think we found our Partner for Nextcloud Managed Hosting
Jaba Hosting https://www.jaba.hosting
We (Heinrich Böllstiftung SH) run a semiprofessionell cloud at Jaba
40 User on a CloudXL with additional memory
one additional CloudXL for another Company in the same house
and one private Cloud S for our Webmaster 
High Speed, No downtime, very fast ticket replytime (under 1 hour)
even outside businesstime
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Many thanks for your feedback.