For Facebook just get the Facebook and Facebook messenger apps.
For making quick edits to Microsoft office documents you can just use QuickOffice but there aren't many good applications out there for creating documents with all the features office has. You could try Kingsoft Office (http/www.kingsoftstore.com/software/office-for-android) as I've heard good things about it but never used it myself. Do some research into it and see what you think.
I also recommend you get some kind of battery saving app, such as battery doctor from the play store.