Weekly, Monthly and YTD calculations

Hi I am so new to this...I need help creating weekly and monthly & YTD total hours. I have weekly spreadsheets that show weekly calculation but I have to manually link the previous YTD. Also, my boss wants a spreadsheet that will show him the total monthly hours (which I have been doing manually as well). Please help me simplify this process. Please keep in mind I am totally new formulas. I have attached sample sheets.

Is anyone out there?