Why does my iPhone 11 have writing at the back

The first symbol, the "CE" symbol is a certification marks that indicates it is in compliance with the EU's health, safety & environmental standards. The other symbol, the trash can with a cross through it indicates that your device is compliant with recycling regulations.

Yep, those are simply the regulatory symbols.

By any chance, when you say "writing with a bin," do you mean "writing with a pen?" If yes, can you possibly take a photo of the back side of your iPhone? Maybe using a mirror? It would help us understand your question better.

They most likely do not have a phone that was made for the EU market, therefore it does not have the regulatory markings on the back. Also just to note, on the iPhone 12 and onwards the regulatory markings for phones made for the EU market are on the side of the phone.