I just set up my Trezor One and I see option to set additional protection with passpharse.
However I heard that while it may make things safer,it can also be devastating if I forget it,or lost it.
Some say it's not recommend to use it,other say it's great extra layer of protection.
I would like to know your opinion.
I would use Trezor and other hardware wallets only with passphrase option because it is not stored anywhere on device and it is much harder for anyone to steal your funds if you lose your wallet device.
It is very important to make good strong passphrase made from several words, write it correctly and back it up in separate location from your seed words.
You can have separate account without passphrase as decoy for holding smaller amount of coins.
Also,I set up my Trezor and download Trezor Suite app for desktop.
I wrote seed words as well as PIN.
I would like to know is that all and am I now completely protected from any kind of threat like hacking or pishing attacks?
You are never 100% protected and phishing attacks are mostly done by human mistakes, not checking if website is correct or clicking link received in email.
Watch what you install on your computer and scan it for malware, viruses and keyloggers before you use this computer for any crypto wallets.
I would suggest that you download Trezor Suite from official website or github page and use that instead of their web version.
Anyone can be victim of phishing so you should pass some free
Phishing Quizzes and learn more how to protect yourself.