I can't save save files in my computer folders, only in Document Cloud

Since yesterday, when i make changes on a PDF file and then try to save it, it won't let me save it in a folder in my laptop, but it only lets me save it in folders of my Document cloud. I havent touched anything, why has this happened and how can i fix it?

Plus, before this even happened, i've been having a lot of trouble just saving files. When i click on save, a black screen will appear with nothing on it, and i cant do anything but close the file without saving the changes. Any idea how i can fix this too? Thanks!!