2019 iMac 21.5" with Fusion drive is dead slow....

I've posted about this before and my problems are only getting worse. I've had 32 support calls, chats, and screen shares with Apple. The most recent was last week and the end result is they told me to shut my computer down, unplug it for 15 seconds, plug it back in for 5 seconds, and restart, when it starts to boot I have to hold down the option and command keys and the P and R key and to do this whenever it slows down. Huh? That's the fix? Yesterday I had to do it 8 times. It does work a little bit faster for about an hour and then it's unusable again and I have to go thru the entire process all over.

This is not just internet-related. I had nothing open at all and clicked on Pages, it took 11 minutes to open. I can only have one Safari tab open at a time and that takes minutes to respond. If I type on a form or something online (like if I'm in my MailChimp account) it will take 2 or 3 minutes for my typing to show up... this is when it's working "well" after the reboot.

I use this computer every day for my job (there is no work-related software on it) I write newsletters and do social media for clients so I'm on either Mail Chimp or Constant Contact or Grammarly or Canva.

Apple keeps telling me to buy a new computer (I'm sure that works for them) but this one isn't even 2 years old! And how do I know that a 21.5" iMac with the M1 chip won't be the same? I don't know if this is the crappy fusion drive or a software problem. I have a friend that has told me to buy an SSD external drive and use it to bypass the fusion drive. But sadly I do NOT know how to do that and don't know anyone who does. And what if that doesn't fix the problem?

The last time I complained about this people here told me to run Etrecheck, which I did and I was told by folks here that everything looked fine. Well, it isn't.

I'm not sure what to do next. I'm a small business person and buying a brand new $3k iMac is a HUGE stretch especially when I don't know what is causing the problem here. I bought this iMac at an Apple store (which is over an hour away) with the assistance of a salesperson who had me list everything I do online and he told me this setup would be ample for what I did. It was for like 6 weeks and then the slow-up started. And it's to the point now where I honestly can't work. I'm going to lose my clients and my livelihood if I don't get this fixed. So far today I've rebooted at least 10 times and it's not even 11 am.

Can someone please help me with some suggestions of where I go from here?

Thanks,

Susan