How can I change the column widths of only a few columns in my many column matrix?

I need the first couple of columns to be wider than the rest of them. Otherwise, the type is too small.

You could increase the first two columns width by injecting this code to your form: 

/* First column */

tr:not(:first-child) td:nth-child(2) input{

    width: 110px;

}

/* Second column */

tr:not(:first-child) td:nth-child(3) input{

    width: 110px;

}

You could either increase or decrease the width value depending on the size you need the fields to have. 

This guide will help you injecting the code to your form: https://www.jotform.com/help/117-How-to-Inject-Custom-CSS-Codes 

I hope this helps.