Thank you very much for your help,
I'm trying to disable it in Settings APK's facilities but does not give me the option of Unknown Origin or Source.
Antivirus'm using those who came to me on the phone: Security, Clean and DU Speed Master Booste.
As for the applications I have installed are: Whatsapp, Citymapper, Google translate, Maps, Instagram, Facebook and Messeger, Uber, London tube, PassWallet.
You command two screenshots of what I get.
Thanks again