Wordpress Edits + WP Cost Estimation Plugin Configuration

I have a one page wordpress, 90% completed. need to configure menu & nav scrolling to various sections, doesn't load smoothly and on mobile menu doesn't go away

Also I have installed - WP Cost Estimation form - need to configure this as it predetermine all the space it may need or not need before any actions and makes the site looks messy
https://codecanyon.net/item/wp-cost-estimation-payment-forms-builder/7818230?_ga=2.49649251.45921573.1519068789-78821127.1515779389