To hide photos, audio or videos on Android you need to have Files by Google app installed in your device, if you haven't installed the app you can download the app and install it by this given link here :- Install App
After installing the app you have to open it and click on safe folder located in the down side of the app to hide your files.
After clicking on safe folder you have to set up lock screen as pattern or pin you can set as you want to remember that pin or pattern.
Now go to your files and tap on the three dot next to that files name you will see the options like this picture.
Then you have to click on move to safe folder option after clicking on move to safe folder your files will be go on safe folder. You want to check the files are in safe folder or not you have to go back from there and click on the safe folder as described below in the image.
To view files in the safe folder you need to put your password which you have taken at the start of the creating safe folder that is pin or pattern you remembered, putting your pin or pattern you will see your hidden images videos and many other files available there.
If you have any queries you can write it in the comment section below.