This article is an appendix to the story below. I added the points that I thought could add values to the original article.
All the credits goes to the original article:
2. Start Open-ssh
3. Create Public and Private Keys. Leave the settings as default.
4. Copy the Public Key to your own
5. Enable folder access for Termux
6. Copy the private key to the Download folder and copy it to your laptop.
7. Copy the files to your computer. (I used AirDroid)
8. Open puttygen.exe from Putty folder. …