Use of pirated or paid apps

Hi Everyone
Good Evening

i am the new member of xda. i had heard lot about using pirated/cracked app in android. In many sites the paid apps are available for free. certain sites restricts use of such app while certain encourages.

i want to know whether it is safe to download such apps in mobile. if YES please suggest the best & safest site for such paid app.
is there any harm to my phone privacy using such paid app for free

thank you

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