Customize Price estimator | Javascript + CSS + mobile friendly

On our website [login to view URL] we use a price estimator which is an implemented app from a charter broker software manufaturer. (Please have a look at it) We need to customize the process and usability. 1. Input: "From" and "To": Some users type in a destination, but don´t select anything from the suggestbox. But we need the airportcode, which is added only if user selects an item from the suggestbox. => Solution: Put placeholder text in the boxes like departure and arrival airport (see picture 1). If User does not selct an item and klicks somewhere else on the page -> delete user input and show Placeholder text again. 2. Date input: If user puts in the 1st leg date, date of 2nd leg stays at old date. Solution: Automaticly set date of 2nd leg to date of 1st leg plus 1 day. After that User has to be able to set date of 2nd leg to same date as 1st leg or later, but not a date before 1st leg. We wanne prevent getting an error, if user misses to set the second leg date or selecting an invalid date in the past in realtion to 1st leg date or exactly same date & time. 3. Presentation of date & usability In addition to solution 2, we would like to present the datepicker in a more modern way and automaticly open the datepicker of leg 2 after selecting a date from leg 1 Please have a look at the PDF File. Explains the project way better!