If you want to hide everything from the public on Facebook, you can follow these steps:
Go to your Facebook profile and click on the "Settings & Privacy" dropdown menu in the top-right corner of the screen.
Click on "Settings" from the dropdown menu.
From the left-hand side menu, click on "Privacy".
Under the "Your Activity" section, click on "Limit Past Posts".
Click on the "Limit Past Posts" button, and then click on "Limit Past Posts" again in the confirmation window that appears.
This will make all of your past posts visible only to your friends, not to the public.
Next, you can also adjust your future posts so that they are only visible to friends. Under the "Your Activity" section, click on "Who can see your future posts?"
Select "Friends" from the dropdown menu.
You can also adjust the settings for other categories, such as your friend list, email address, phone number, and more. Click on "Edit" next to each category and choose who you want to share that information with.
By following these steps, you can limit who can see your past and future posts, as well as other information on your profile. Keep in mind that some information, such as your name, profile picture, and cover photo, will still be visible to the public. If you want to change this, you can edit your profile and cover photos to only be visible to friends or only to you.