Can I upload more than one file at once?

Yes, it is possible. Instead of uploading the files one by one, you can upload a folder. First of all, you have to compress the folder you want to upload, by clicking on it with the right mouse button and selecting Add to archive. Once the ZIP file has been created (attention: it must be a ZIP file, not a RAR file or other compressed formats!), you can upload it with the drag-&-drop tool or selecting Add an activity or resource in the desired section, then choosing Folder.

(last update: 03.08.2018)