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Besides, as Porf recommended, please suggest one topic at a time though, not all 3 
(We may think about the other 2 ones after finishing one of the 3 topics.)While waiting for DS to suggest on of the two topics.......
You should start with this topic first. It's the easiest and shortest topic on PGP (Android).
Note: As for the PGP keys inside the post, I'm not sure if it should be replaced with the respective translators PGP keys (if have one). Because the main author might not be there to reply in different local boards or help users or encrypt or decrypt messages using PGP.
-DS 🧛♂️
Out of the proposed topics about PGP, I agree that this is the most useful for many people (roughly 3/4 smartphone users are Android users) and the easiest way to learn fast how to encrypt/decrypt messages.
I also like the idea of replacing the code in the OP with our own PGP code.
As other members also chose this topic, let's add it to the list of translations in progress