I can't save any documents(macbook pro)

Hello!

I have a macbook prSince yesterday,my mac can't save any documents such as keynote.It says that it can't save it and i tried to export the document to power point or to another type of program and it says the same.I also tried to save documents in another programs and it's the same.So the problem seems to be in the computer.

Besides,I can't paste photos since yesterday too.Even,if they are from Photos or I do it from the program.It says that it can't be pasted.In any program too.

So,if you have any idea of how to solve this problem I will be grateful.

Thank you for your time

Marta