you need to secure first your private key or your seed phrase/ or you can send it to your email/Yahoo to be secured because it is very helpful to you to recover your wallet.
You should never do that and never encourage others to do it. Storing your private keys/seeds online (emails, cloud storage...) isn't any different from storing your coins on exchanges/web wallets, actually, it's even worse.
The best way to keep your pk/seeds safe is either by storing them digitally on an air-gapped device or physically by simply writing it down on a piece of paper and hide it in a safe place.
Exactly, because everything online can be hackable and email accounts are prone to compromise by hackers, so it's not advisable to store your seed phrase and password there. But instead, store it offline that is safe from any disaster that possibly comes.
Regarding the OP problem, I think there's nothing we can do if OP didn't back up the seed phrase, reformat means it will clean up all files on your phone especially if that is a hard reset of your phone, it wiped it all and nothing left aside from factory default. We should be responsible for keeping our wallet credentials and treat this as valuable stuff, digital currency is very crucial to hold and any time it can be lost.
