Will it be safe to create a private key by encrypting absolutely random letters in SHA256, for example 'sdfguhiuwrUISDHGNIUXHIUCV238778dfvhgjhuidsahgfiu', encrypt these random letters and numbers in SHA-256 and use the resulting private-key for bitcoin? I can do this with the Internet turned off, I can encrypt the absolutely randomly typed phrase 'sdfgdhfsuyghuHUDUIHGHIUG878yet7y8bchxujxcbvhidsafhguihuq' in SHA-256, write the received private key and use it to use Bitcoin? Why use some kind of generators, when you can encrypt any randomized characters typed on the keyboard, and use the resulting private-key for bitcoin? After all, in fact, no one will know the phrases with the help of which the private-key was created, and the only way to lose it is if someone other than me gets access to the private key.
In creating bitcoin wallet, the only things which I could suggest is try to use Electrum, by this things as long as you have the private key, phrase and password your bitcoin will be safe, as long as you do back up for it. Or you could also Hardware or multibit wallet where these things are good to use so far.