I have no idea, which subforum the question may be. Well. If I insert, for example, sd card to th mac and drag a file from there to desktop, then I get a file on desktop and still have a file on sd card. It's like a copy. If I open finder and for example from the category music I drag a file to the desktop, then that file completely moves to a desktop and it no longer exist in finder. I need that the file stays in finder and also exist on the desktop, in the same time. Like with sd card. Is it possible? For me is comfortable to use a file on desktop for a work and then just delete it there if I will not need it anymore. But in finder I will still need that.

You're doing two different things there, that's why the different behaviors.. - When you drag a file from an SD card you're going from one disk [external] to another [internal] -- in that case macOS automatically copies the file to the new disc, leaving the original in place. [If you want to move it and remove the file from its original location on the SD all in one step, Command-drag it [hold down the Command key and drag it] to do that]. - When you drag a file from one location [folder] to another location [folder/desktop*] on the SAME disk, macOS moves it, so there's only one copy of the file, in the new location. If you want to copy it, leaving the file in its original location [folder] with the copy in the new location [desktop], Option-drag the file [hold down the Option [Alt] key and drag it] to do that. * Note: Files you see on the desktop are actually in the Desktop folder in your User folder [in the main HD]

Yes, option key helped, thanks! But when I wanted to listen to it, then apple music appeared. Can I listen only with apple music that file? When I dragged from sd card to desktop, then it just started to play, no need was for apple music. Or how can I listen my files? Right click only with pop-up menu or 1click or 2 clicks after each other also will play the file?

On my system if I select an audio file and just hit the Spacebar it plays. I don't have Apple Music [the newest version of iTunes] on my system -- I have the version of iTunes that comes with Mojave -- so I can't tell you if that newer version would change that behavior.. You should also be able to set which application opens up when you double-click an audio file [in Finder]: - Select the file and hit Command-I [Get Info] - In the Get Info window, under the "Open with" tab, select the application* you want to open & play that file [when you double-click it]; - If you want that application to open/play ALL audio files [when you double-click them], also click Change All... * Usually the default application is iTunes (which is now called Apple Music], so that's where you should be able to change that..

Yes, that's correct. I chosed audio file and hit the spacebar and my file plays, too in catalina. Thank you for that! But I have another question. If, for example, firefox is open, and I have opened a finder as a second window and want to get a file to desktop from there, must I close firefox window, or can I have any other chance to "open" the desktop? I mean, the finder window opens as small and around it a desktop, no problem to drag from there to the surrounded desktop. Otherwise, if firefox or anything else (another window) is opened, then that large one is surrounding of small finder window. But not desktop is seen. While I typed this letter, I can't type anymore and when I hit the spacebar, this forum window changed to its half size and desktop appeared. I can't scroll it to see that letter in bottom. Then I didn't know more to do than tap to the x of another opened window, but instead of disappearing, it stayed and the forum window got big full screen again. What happened or what I did? Before it I checked out above left a full screen and half screen options (yellow or green marks), but I didn't tap there, as I don't know how to get half screen and how to get rid of that.

And when I closed the two windows I mentioned above, they like disappeared to the right and "first page" came like from left. What is that now? How it came and how can I get rid of "the new system"... ?

If you want to download a file from a browser to the computer just use its download method; in Safari & Chrome you'd right-click on an item [like a graphic] and select "Save to Desktop" -- I don't use Firefox but I'd imagine it works the same way. As to the rest, I can't understand your description at all. If you need to better understand how to work with windows in Finder check out Apple Support -- once again, a simple search for "macOS windows in finder apple support" turned up this support page: https://support.apple.com/guide/mac-help/work-with-app-windows-mchlp2469/10.15/mac/10.15