Website is slow – hosted on wpmudev

Hello,

since i moved my site to wpmu-host it’s really slow.
You can see the “development” site here: https://biog.at/uebersicht-ersatzteile/wangen-biomix-pumpe/ (It’s also not the fastest, but OK).
And the live-site here:
https//biog.at

Do you have a advice for me where to bottleneck is?

Thank you in advance and best regards,
Niko