2019 iMac 21.5" 4k runs painfully slowly

I have four basic issues with this 2019 iMac 21.5" 4k.

1) It runs so slowly as to render it almost unusable.

2) There is an issue with the App Store and Numbers, Keynote, Pages, and IMovie, where those programs insist on partially downloading themselves only to get hung up and not complete installation.

3) It will not update to IOS 15.4.1. I have tried several times, and it always stops at "30 minutes remaining." I have tried the suggested remedies online. With Disk Utility, I received these messages with "Macintosh HD- Data:"

warning: inode (id 1657965): dir-stats key xf does not exist, despite internal_flags (0x8412)

warning: inode (id 1662640): dir-stats key xf does not exist, despite internal_flags (0x8412)

warning: inode (id 1662812): dir-stats key xf does not exist, despite internal_flags (0x8412)

warning: inode (id 1668380): dir-stats key xf does not exist, despite internal_flags (0x8412)

warning: inode (id 1668688): dir-stats key xf does not exist, despite internal_flags (0x8412)

warning: inode (id 2162923): dir-stats key xf does not exist, despite internal_flags (0x8512)

warning: inode (id 2282749): dir-stats key xf does not exist, despite internal_flags (0x8012)

warning: inode (id 79163037): dir-stats key xf does not exist, despite internal_flags (0x8512)

warning: inode (id 79163272): dir-stats key xf does not exist, despite internal_flags (0x8512)

warning: inode (id 79163469): dir-stats key xf does not exist, despite internal_flags (0x8412)

warning: inode (id 79163580): dir-stats key xf does not exist, despite internal_flags (0x8112)

warning: inode (id 89251640): dir-stats key xf does not exist, despite internal_flags (0x8012)

warning: inode (id 185168202): Resource Fork xattr is missing or empty for compressed file

warning: physical_size (1773568) of dir-stats object (id 82928155) is greater than expected (0)

warning: descendants (60) of dir-stats object (id 83015994) is greater than expected (22)

warning: descendants (60) of dir-stats object (id 102104092) is greater than expected (58)

warning: descendants (14) of dir-stats object (id 102637343) is greater than expected (13)

warning: descendants (7) of dir-stats object (id 1587653) is greater than expected (6)

warning: physical_size (20148224) of dir-stats object (id 1587653) is greater than expected (86016)

warning: physical_size (2244657152) of dir-stats object (id 1587657) is greater than expected (2240114688)

warning: descendants (301) of dir-stats object (id 100814633) is greater than expected (298)

warning: descendants (63) of dir-stats object (id 100814698) is greater than expected (62)

warning: descendants (1701) of dir-stats object (id 1609829) is greater than expected (1556)

warning: physical_size (1804341248) of dir-stats object (id 1609829) is less than expected (1813729280)

Checking the extent ref tree.

Verifying volume object map space.

The volume /dev/rdisk2s1 with UUID E7CA8E94-A334-4C31-ABFE-E6B65DC12FAB was found to be corrupt and needs to be repaired.

Verifying allocated space.

Performing deferred repairs.

The volume /dev/rdisk2s1 with UUID E7CA8E94-A334-4C31-ABFE-E6B65DC12FAB appears to be OK.

File system check exit code is 0.

Restoring the original state found as mounted.

4) I have read that running the OS from an SSD often fixes the issue. Exactly how does one go about it? What needs to be transferred to the new external drive? Are there settings I need to alter to make everything run from this new external drive?

Thank you.