Unable to download images or screen shots to desktop

If I'm not mistaken, the keystrokes for creating screenshots in 10.13 are (⌘⇧3) command-shift-3 (or 4). Not control-shift...

Have you restarted your Mac lately?

Rebooting is the best first step in troubleshooting.

If a simple reboot of your Mac doesn’t fix things, see if the problem still happens in safe mode.  Use a wired USB keyboard for this. If you have the Magic Keyboard, plug that into the Mac with its charging cable.

How to use safe mode on your Mac - Apple Support 

Safe mode will often correct weird software behavior by forcing the OS to clear caches, do disk repair and other self-maintenance and housekeeping and temporarily disables third-party mods.

Do you have the same problem while in Safe mode?

You can exit safe mode by restarting your Mac normally, then reevaluate the problem.

Command-Shift-3 (or 4) should save a screenshot to the desktop, but the fact that other images can't be dragged there hints that something else is amiss.

Have you turned on Stacks in the Finder?

Stacks is a feature that automagically collates items on your desktop into logical groups. One of them is Screenshots, where it creates a stack (kind of like a folder) for screenshots to help keep your desktop uncluttered.

Check Finder -> View -> Use Stacks to see if that helps.

> Sorry I can´t find Use stacks under view where is it specifically?

Right here:

I may be running a later OS version than you, but Stacks were introduced back in 10.5, IIRC, so it should still be an option for you.