What is the best methods to protect altcoin from hacker?
take care of your private key, passwords and dont click any suspicious link that has been sent to you through pm, shared on any social media sites, etc. the only reason why hackers have the access on your account is because they successfully get your key.
That's why obviously the best way of securing the wallet is to keep the keys on printed paper somewhere but nowhere on your PC. I think that keeping passwords in Telegram is also safe, though, since it is encrypting messages. Of course, in this case you have to be sure your phone will not get stolen. Anyway, it is also worth to mention that the wallet website better be bookmarked or saved somewhere from the email messages instead of being accessed via google, because there're lots of very good fake websites, that can track what you type and type that on the real website soon after that. In general, it is important not to tell anyone any information that might help accessing you wallet. And you'd better put strong passwords on every account you have in case you hold some info on passwords online.