Nextcloud allows you to share files, documents, pictures and calendars. You can either access the files through your browser or install a synchronization client on your computer, which - like Dropbox - transfers all (or only selected) files to your own computer. Furthermore, OnlyOffice integrates the possibility to work together online on files, as known from Google Docs.
The university's Nextcloud installation can be found here: https://next.kh-berlin.de - for department VK: https://vk.next.kh-berlin.de
The access data is managed by the respective responsible person in the department.