I want to learn how to fix the parts of epson printer

@gulmuhammad each printer has its own issues. If you are looking for general repair I would get as many manuals as possible and look for common things. Use the iFixit guides and check each one of those. Look for similarities in construction and similarities in parts and yes, errors too. Epson Printer

If it is specific to a certain printer you could try and get the service manual. Printers are a pain to repair. Parts are had to get and lots of plastic pieces that seem to never get back together properly.

Here are a few resources to learn from. More are available all over the internet

Print Head Repair SecretsEPSON T 50Troubleshooting Repairing Computer Printers 2nd Edition

I have an antique Epson all in one, and a few years ago it quit printing. It turned out to be a broken wire in the cable from the lid into the printer. It flexes every time the scanner is opened. I replaced it with a more flexible wire and it's been working for years since.