Mobile phone does not work iframe position: fixed

Problem. I have a React application. I load an iframe (the iframe site has its own menu in the bottom panel) and when viewed in a mobile application, my iframe site stretches and hides completely under (my site navigation – screenshot) and partially under (iphone browser tab bar – screenshot).

enter image description here

(iframe site navigation – screenshot) has position: fixed; bottom: 0; and I can’t edit these values ​​because it’s an iframe.

If you look through the chrome developer panel, then there are no problems and everything works.

If this is possible, please tell me how to fix this problem?