... I mean, without using a computer, in other words, how to generate a paper wallet using only paper and pen, or is it impossible?
How is that even possible , if it was possible, everyone then can get Private key just from the Public key which is your BTC adress
No. It is very difficult to determine a private key based on the public address. It however is very easy to determine the public address based on the private key.
In theory the public address can be manually calculated based on the private key however it would not be recommended to do so because if you make a mistake and have an output of an incorrect address then you could end up sending money to an address that you do not control the private key to