How can I add 2FA “2 Factor Authentication” in my 
app?
May be firebase phone authentication help you
You can use eFeMail extension so that on login you create a random code and store it in TinyDB or whatever then send it in an email with the extension after providing the destination email and the user enter it in your app and if it’s equal to the one you stored before then validate login, it’s not very hard you can do it. 
For SMS i think it would be a bit hard but nothing is impossible and i’ll try to think about a solution for it and tell you.(Try with Firebase)
Mark as solution if it helps 
Hi, @youssef_achour,
Your reply was helpful for me but I want a 2FA that has a QR code and if we scan it in a 2FA app it will show the code.
In the QR code it has a linked URL example = otp://xxx_id=123456abcd_provider=abc
If we scan In a 2FA app it will show us the code. So how can I do that?
Same method i mentionned above, but just after generating the random code or link or whatever use the QR Code component to create a QR code for it and after getting the link either insert it as image in your email body HTML code or as attachement, of course send the email using eFeMail extension and don’t forget to enable isHtml parameter if you’ll use HTML codes. And to scan it with the app use Barcode Scanner component (it scans both barcodes and QR codes).
Hi, @youssef_achour
Thanks for the reply but can you show me the steps to do it? I actually don’t know how to make it.
you can create qr code of random text and then the user can scan it.