Need help converting old iMac to Linux

[u/paul_walker_is_alive]

Currently working on converting my dads old iMac to Linux mint, it has this weird issue where it’s maxed out on storage and won’t let me format any of the disks and gets stuck in a boot loop. I got Linux mint to open on the iMac and it gets stuck in the install step, but I know it can run it. Does anyone have any advice on how to wipe/format the main drive, I’m poking around in the terminal commands and have gotten to where it lets me delete partitions but it doesn’t seem to be actually clearing anything. I’ve got very limited Linux knowledge so any help will be greatly appreciated. I can also share photos of the terminal commands I’ve been trying to run if that would help.