How to prioritize firefox shortcuts over xfce key shortcuts

I would like to use the Firefox shortcuts for e.g. swap between tabs. But when I use CTRL+SHIFT+Pageup, then xfce will change window size. Is there any way to change the priority of shortcuts, so that when I am in Firefox, it will preferably use the Firefox shortcut and not the xfce shortcut?

I am using Linux Mint 19.3, xfce4.14

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Author: Mara 01010011