Setup Excel Spreadsheet for Financial Projections

I have a small business, that gives me the sales for each day of the week. I want an excel spreadsheet that will enable me to use this information more effectively. Currently I have three years of sales data, and I want to be able to have it setup so that this information can be used to show weekly comparisons, daily comparisons, YTD figures etc, as well as things like a 6 week average per day of the week. I already have made a sheet that does this myself, but it is not done efficiently and involves lots of long-winding ways of calculating information etc. I need someone who can streamline this sheet, and make it easy to put in future data as well. The sheet I am using now is attached, as you can see, it mostly works, but is not high quality, especially when presenting to my boss, and want it a bit simpler to use and update. At the moment I manually put the weekly data into the "data" tab and it spits out the rest, but thinks like the graphs don't update without a lot of work every 12 months.