@DaphneWerz - I'm still not sure why this is happening, but I am hopeful that the content is intact, and you can at least use the files. I would try changing the extension of one of the files from .file to whatever it is supposed to be. So rename a downloaded file such as "Lecture x.file" to "Lecture x.pptx" if you think it's a powerpoint (or .docx if you think it's a Word file, etc.) To do this, first display file extensions in the File Explorer if you're using Windows. (Open File Explorer, click the View tab, select Show > File name extensions.) Then, rename the file and change the extension. (In File Explorer, click to select the file, press F2 on your keyboard, and enter the new name.) After changing the extension, try opening the file.