Modal dialogues on the phone – back button

I have a site where I have a small gallery. If you click on the image, a description of the team member and more pictures are displayed.

On a normal desktop, I thought about implementing the extra information with a pop-up (or some kind of lightbox). Which is somehow okay because the user either clicks on the X or presses the ESC key. And the dialogue is closed.

On a mobile device, the content is displayed in the same style. However, due to the limited screen size and the amount of content in PopUp, this more or less blocks the entire screen. Sometimes it does not even fit on a screen and the user has to go up and down.

Now the main question is how to close this popup. There is no ESC key on a mobile device. If the user does not find the close button (s) easy, he closes it with the back button. With the back button, however, you also leave the website and return to the previous one.

Any ideas on how to display this additionally Information right?