When i tested it on my iPhone,i pushed the button and it launched the facebook application, but it navigated to the "news" and not to my page.
How can i fix it?
I'll suggest Gerry's advice, too.
Using a native browser.
"launch url" command isn't reliable in this respect.
It can open Safari and your desired Facebook page,
but if the user has installed native Facebook app then it'll navigate to it with the user's News screen.
Plus, I don't want the user to leave my app just to look at the social media link of the customer.
So, I integrate a dedicated browser card in all my projects.
Then, open the customer's {owner of the project} Facebook, Twitter, LinkedIn, etc. pages in that browser card.
In result, the user won't leave the app and go back to previous page just hitting the back button;
and the problem you've mentioned is not issue anymore.