imac 3.6 GHz Guard Core Inter Core i17 very slow

if it was me, I would use the existing internal drive as "external" storage and load your current data on the SSD. but in your report, it also says your HDD "appears to be failing". so I would strongly recommend that you maintain a full backup if you use that drive for storage, as the HDD could fail soon.

and FWIW, you could always use the SSD as a boot drive and keep your lesser used data on a separate external HDDs. I personally keep very little on my local drive.

the main issue as I see it is that you are running Ventura on a Mac with a very slow (5400 RPM) mechanical hard drive. those Macs do not perform well on modern macOS. the most cost effective way to speed things up would be to install macOS on an external SSD and run the Mac from that. to implement that, please see this informative user tip: Use an external SSD as your startup disk with your iMac or Mac mini - User Tip

you're welcome. :)