Help with SharePoint connection issues

Hello,

Quite suddenly, and now frequently, our spreadsheets on SharePoint are having difficulty saving. This was only a rare occurrence previously, but now happens to us regularly. It is so bad that we will have to stop using SharePoint if we can't figure out why it is doing this. Can anyone provide some advice as to what could be going on? We get errors saying we can't connect to the server and that it could be our internet connection. I highly doubt it's our internet connection as it is happening on many different connections all of which don't have problems connecting to other things. Do we have too much saved on our SharePoint perhaps?