Memory is something else then storage, i don’t think your storage is already full with only 20 apps in such a short amount of time.
I think you are talking about the (RAM) Memory which is (only) 512MB, and will get allocated fully by the operating system, even with only 2 apps installed, that is just how linux works with its available memory and is completely normal.
But if you want to save insight data you can click the
... icon on the insight page behind any capability of a device, and select
or use this app to save all insights as an csv file.
If homey is already unstable, then there is something else wrong, and you can better take contact with email@example.com, as this is just a Community Forum.