"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.