Hi,
In odoo  there is no default option to fix the column size. You need to make customization and need to add some CSS style in your code to make the column fixed.
below are some examples for the CSS style you can add for some classes to make the column fully readable
.text-truncate {
    overflow: visible !important;
    text-overflow: ellipsis !important;
    white-space: normal !important;
    /* vertical-align: top !important; */
}
.o_list_renderer .o_list_table tbody > tr > td:not(.o_list_record_selector):not(.o_handle_cell):not(.o_list_button):not(.o_list_record_remove):not(.o_list_record_open_form_view) {
    --fieldWidget-display: block;
    display: table-cell;
    overflow: visible !important;
    text-overflow: ellipsis;
    white-space: normal !important;
}

.o_list_renderer .o_list_table .o_data_row:not(.o_selected_row) .o_list_many2one .o_field_widget:not(.o_row_handle):not(.o_field_handle):not(.o_field_badge) span:not(.o_m2o_avatar){
    display: inline;
    max-width: 100%;
    white-space: normal !important;
    overflow: hidden;
    text-overflow: ellipsis;
    vertical-align: top;
}

Or else you can add your own style as the way you needed

Hope it helps