If you have access to GarminExpress then the device isn't 'soft-bricked' in the usual sense because GE uses Mass Storage Mode for communicating with devices. So you should also be able to browse the internal file system using Windows File Explorer. Firstly, in Windows Device Manager go to File Explorer Options (or Folder Options in earlier Win OSs) > View and set it up like this:
Spoiler: Click for Image
[Only registered and activated users can see links. ]

That way you'll have access to the normally hidden .System folder. Now make a full backup copy of all the folders and files in the internal memory.

Before you go further and maybe waste time deleting recent files unnecessarily, please state what's now happening on attempted start up, e.g.: is it sticking on the logo splash screen, showing a white screen, bootlooping, stuck on 'software loading' message ... or what?