If this help you, here and here are to good tutorials that slowly goes into “everything emacs”. My advice is to expand one step at a time, see what works for you and what not.
As to email - mu4e is a good starting point. Most of the setup is actually outside of Emacs (isync and msmtp) and interface is kinda familiar to what you can find in other email clients.
There are importers for most of the password storage options. I would recommend separate database for import and then merging import db with your actual database, backing up everything before.
Or you can use something like Yubikey as a second layer. Don’t know if that works on mobile.
As many said combination of KeePassXC on computer and KeePassXD on android. I sync file with syncthing. For security I have setup three word passphrase, made of words representing unique stuff that was on my desk at the time of creating file, words are connected with symbols not spaces. Even if someone gets my password database file, it will be useless for them.
KeePass has many adventages:
You learn all life. Just take your time. Emacs won’t go away anytime soon ;)