CMS panel opening very slowly despite fast internet connection

I wonder for what reason the Kirby panel could slow extremely down. Sometimes it takes a half minute until I get the file list loaded in the panel, while all news pages in the internet load extremely fast. Are there any known issues?
I also wonder if that could also influence the page speed.
Because sometimes it loads immediatley all media, sometimes it seems not able to load the page. Friends told me about a minute of waiting time when they open the webpage.
I found a similar thread:

Thanks for help

What sort of calls are you making in the Panel? How many pages are you querying and how many files?

Are you making any calls to $site->index(), maybe even multiple times?