Hello @kangqi and welcome to the community. Please have a look to the #start-here category when you have the time.
Retry with the command line, but using reinstall instead of install
sudo dnf reinstall https://mirrors.rpmfusion.org/free/fedora/rpmfusion-free-release-$(rpm -E %fedora).noarch.rpm https://mirrors.rpmfusion.org/nonfree/fedora/rpmfusion-nonfree-release-$(rpm -E %fedora).noarch.rpm