How to set col width in a field list

I am using the twenty seventeen theme, and in my form with ID:1 I have a field list with ID:16. The form is included into a page using the Elementor editor.

I am trying to set the column width of a certain column in this form and this field only, by adding the following code to the theme customizer:

body #gform_wrapper_1 .gform_body .gform_fields .gfield .ginput_list table.gfield_list colgroup col#gfield_list_16_col3 { width: 10px; }

That doesn’t seem to change anything to my form.

I am still a new user of CSS, so forgive my ignorance. Why does this not work?

Can you share a link to the page on your site where we can see the form? Thank you.

sure: http://wp.ssg-brugg-windisch.ch/vindonissaschiessen/anmeldeformular/

Is “Jahrgang” the column you want to target? If so, you can use this CSS in the Customizer, or you theme functions.php file:

body .gform_wrapper td.gfield_list_16_cell3 input {
    border: 1px solid red;
    width: 10em!important;
}

You can set the width to whatever you like, and remove the red (that was just showing what I was targeting). Let us know if you need anything else.