If you want to impose restrictions on your child or you feel that you are spending too much time on Facebook or other addictive websites, such as OLX or Mobile.de, you can restrict access to them on your iPhone in just a few moments. 
Not infrequently, we realize how problematic it is that we spend a lot of time on the phone, on a social network, on a shopping site or an online platform specific to any other field. Fortunately, if you realize you have a problem, you can do something about it. Moreover, you can use this mechanism to restrict your child's access to a web page or service that I consider inappropriate.
How to block a site on iPhone or iPad, whether it's Facebook, OLX, Mobile or something else
Apple allows you to block access to a webpage in just a few minutes. Because only a few simple steps are required, you can do it several times a day. You may be able to block access to this setting with a password, but it is not required.
To block access to a webpage on your iPhone without any additional software, simply go to Settings and Settings in the Usage Time section, as you can see in the screenshot below. There you can also define an access code if you want to define these restrictions on your child's phone or tablet, for example. To do this, choose "Use a code for" Use time ".
From the menu, to define the actual restrictions, choose Content and Privacy Restrictions. Go to Content Restrictions on the new setup page and tap at the bottom of the web Content screen. Check the Restrict Adult Websites top and tap Add a website to the Never Allow section.
In the case of Facebook, you can type facebook.com, but also enter m.facebook.com to prevent access to the mobile version of the service. Repeat the process for any other web address. The changes take effect in real time, and to delete a previously entered web address from there, all you have to do is swipe right and left over its name.