Published report terrible performances - datasource from sharepoint list

Hello.
i'm here to ask for help.
i have a Power bi dashboard that uses a SharePoint list as data source.
when i publish it on the portal i can choose when to refresh so I assume that I'm not in direct query but in import mode.
the fact is that when i open the report on the portal/app visuals are really slow (they took up to 3 minutes to display and being populated)
when i open the same report on my personal computer it takes seconds
the performance analyzer doesn't highlight anything too big:

what i could be to destroy like that the performances? what can i do?