To begin, navigate to the Toolbar > Edit with Elementor > Open the Navigator for easily locating the widgets https://elementor.com/help/navigator/ > Edit or remove the Divider widgets:
Next, open the first column's Style tab > Open the "Border" section > Edit or remove the right and left border width:
The border length depends on this Spacer widget:
Please check this guide for further information:
Guide to Vamtam Elementor Builder