There are different ways to reduce the file size of Excel, you could zip the file, save as xml, or compress the file.
But first, look at this file's size:
Note: You could just right click on the file, and choose zip or compress in the options showing. However, you would need a program like WinRAR, WinZip, or any other program that zip. If that suits you perfectly, please do.
Open the file, click on the things that make the file large (in this case the picture).
With the picture marked, click on format (1), and then compress picture (2).
Note: Repeat these steps on all the pictures, or other.
Use "Save As" to save the file in .xlsb format
In conclusion, the size reduction might not be much, but it is something.