Unsolved problems about my iMac

Hi all,

3 months ago i've posted this question about some strange issues about my 2019 i9 iMac with 512 SSD and 8 GB's of RAM, but i couldn't get any replies. So i called Apple but after 30 minutes of phone support they didn't have a clue about my problems. To try something new, i formatted my mac with a clean install but everything is still the same. So here i'm posting it again.

Issue 1.

Files are 'sometimes' showing up late in folders.

For example, when i download a file to my downloads folder, i see the download is complete in Safari but i can't find the file in my downloads folder. Then I wait for a while and see the file 1-2 minutes later. It doesn't have anything to do with sorting the downloaded files. Same thing happens when i save a file to desktop or some other place from Photoshop or other software.

But the strange thing is when i save a file from Photoshop and then click import on Photoshop. I can see that file on import window. But i can't see it on desktop.

Here you can see a downloaded file is showing up in one place but not in the folder.

Issue 2.

"Sometimes" copying of a file keeps going for hours.

When i try to copy a file or files from a folder to another, the process stucks at 100% and waits like that for 5 minutes, 30 minutes or forever. Even if the total size is 5MB or 20GB, it doesn't matter.

Issue 3.

"Sometimes" preview doesn't work.

When i click on an image or a pdf file and push space for a preview a blank window opens and the loader keeps spinning.

Issue 4.

When i download a zip file, even if it is a 1MB zip file it takes 2-3 minutes to unzip it.

And finally a common issue is that i find this iMac working not fast as expected. I used to own an iMac 2017 with i7 processor and the old one was faster than this one. I'm a videographer so i'm mostly working on editing, rendering and etc.

So any ideas about these problems?

Thank you.