grid-template-columns: minmax(min-content, 20%) 1fr 1fr;
grid-template-rows: 1fr 1fr;

The minmax() function defines a size range greater than or equal to min and less than or equal to max. If max is smaller than min, then max is ignored and the function is treated as min-content
Row One, Column Two
Row One, Column Three
Row Two, Max Content Column One
Row Two, Column Two
Row Two, Column Three