Delete photos on my phone without them being gone on the other phone?

I bought an iPhone 11 two days ago and first I didn't have the pictures from my old cell phone on it but then everyone came. Then I tried to delete them and then they were gone on my old cell phone. And I really only wanted these pictures on the old cell phone so that I can do everything from the beginning with the new one. And yes these pictures are very important because they have a lot of nice memories. And no, I can't save them on a stick because my laptop is unfortunately broken. So is there any other way to delete my pictures without them being gone on the old phone?

You can load them into a cloud or there are also USB sticks for your smartphone

Ah ok thanks