There is no secure folder in this device...i can't be hide my personal details from the storage.
"Nokia 6" has so called "Stock Android" or "Pure Android" OS, that is one of the main marketing arguments. "Stock Android" does not offer a secure folder app nor option. So, you are basically upset against your self, you should have bought a device that has customized OS. However there are a huge amount of "Secure Folder" apps available, likely some are free, but the price of the paid apps is just pocket money.
The meaning of the following is unclear: "Other thing is the nokia 6 device is slowing with other devices...there is no improvement."
It looks like you're new here. If you want to get involved, click one of these buttons!