Sudden increase in file size Excel 2019

Hi ...
Suddenly my Excel file increased in size from 370kB to 12381kB.
That's 33 times greater than the day before.
Because of that the workbook has become much slower, even though I have 18GB RAM and an Intel i7 processor.

Does anybody here ever experienced something similar to this?
What's your suspicions of what can cause such an increase in file size?

I did some checking if a background picture could be an asset to the workbook, but it didn't, so I removed it.
But is it really removed?

Any ideas are received with a sincere thank you.

That helped a lot!
Reduced to a mere 3MB.
Thanks.

370kB and 3MB. is not good result. Try to find any object on the sheets. Could you public this file?