However, after I ran the sudo pacman -Syy gnupg archlinux-keyring manjaro-keyring command, it asked me to run the command sudo pacman-key --init. So I ran it, and the again ran the previous one (sudo pacman -Syy gnupg archlinux-keyring manjaro-keyring). It gave a lot of errors:
:: Synchronizing package databases...
core 170.6 KiB 145 KiB/s 00:01 [########################################] 100%
extra 1901.8 KiB 1041 KiB/s 00:02 [########################################] 100%
community 6.6 MiB 1218 KiB/s 00:06 [########################################] 100%
multilib 177.4 KiB 949 KiB/s 00:00 [########################################] 100%
warning: gnupg-2.2.29-1 is up to date -- reinstalling
warning: archlinux-keyring-20210802-1 is up to date -- reinstalling
warning: manjaro-keyring-20210622-1 is up to date -- reinstalling
resolving dependencies...
looking for conflicting packages...
Packages (3) archlinux-keyring-20210802-1 gnupg-2.2.29-1 manjaro-keyring-20210622-1
Total Installed Size: 11.43 MiB
Net Upgrade Size: 0.00 MiB
:: Proceed with installation? [Y/n] Y
(3/3) checking keys in keyring [########################################] 100%
downloading required keys...
:: Import PGP key FC1B547C8D8172C8, "Levente Polyak <anthraxx@archlinux.org>"? [Y/n] Y
:: Import PGP key 6D42BDD116E0068F, "Christian Hesse <arch@eworm.de>"? [Y/n] Y
:: Import PGP key 428F7ECC7117F726, "Helmut Stult <helmut@manjaro.org>"? [Y/n] Y
(3/3) checking package integrity [########################################] 100%
error: gnupg: signature from "Levente Polyak <anthraxx@archlinux.org>" is unknown trust
:: File /var/cache/pacman/pkg/gnupg-2.2.29-1-x86_64.pkg.tar.zst is corrupted (invalid or corrupted package (PGP signature)).
Do you want to delete it? [Y/n] Y
error: archlinux-keyring: signature from "Christian Hesse (Arch Linux Package Signing) <arch@eworm.de>" is unknown trust
:: File /var/cache/pacman/pkg/archlinux-keyring-20210802-1-any.pkg.tar.zst is corrupted (invalid or corrupted package (PGP signature)).
Do you want to delete it? [Y/n] Y
error: manjaro-keyring: signature from "Helmut Stult (schinfo) <helmut.stult@schinfo.de>" is unknown trust
:: File /var/cache/pacman/pkg/manjaro-keyring-20210622-1-any.pkg.tar.zst is corrupted (invalid or corrupted package (PGP signature)).
Do you want to delete it? [Y/n] Y
error: failed to commit transaction (invalid or corrupted package (PGP signature))
Errors occurred, no packages were upgraded.