manipulate dropdown when cell value changes

Good day,

I have a dropdown menu in column A. Cell A1 says "All", A2 is 1, A3 is 2....A10 is 9. This is hidden

My actual dropdown is in C1. Lets say I have already selected "7". So cell C1 displays "7". Here it comes now:..

If I change the value in cell E1 (any value), I would like the dropdown display in C1 change to "All". So it must be like I manually selected "All". Maybe this would be important to add..The value in E1 is also a dropdown.

Any help would be appreciated..please. Thank you for spending time with this..

Excellent!!, thank you very much!