Bug fixes on PHP application (Clinic management system)

The app is a clinic management [login to view URL] is build in PHP with MySql database. I need very urgent the modifications. The tasks are: 1. Possibility to modify the appointments. There are cases when a patient makes appointment for a service, but performs other, or more services. The field exists, but the modification of appointment cannot be done. 2. In the appointment daily calendar, if you make two or more appointments at the same hour, in the same room, only one is displayed. This issue must be fixed and display all the appointments. 3. Add for a column in the table with doctor fees and print the inserted result when a payment is made. Room Rental is a payment option where you can choose the amount that patients are paying to the clinic. The task for this issue is to develop a column in the Doctor fees existing table. The column name will be “Doctor Fee for RR” and will be writable for the users, in order to introduce the amount to be paid. When a payment is done using the Room Rental option, the price of the selected service should autocomplete with the one introduced in the table. The field should not be looked. In some cases the operator may decide to pay more or less, so the amount is for orientation only. 4. Modify the patient payment section – currently the VAT for materials is not taken into consideration when patient performs a payment. The VAT of the material has to be added to the price. The VAT is stored in the DB and can be modified from the application. 5. Invoices (the section need some bug fixes) - Make a section where to store all issued invoices, and offer the possibility to filter them after the clinic and issuing date. - Number of the invoice must start from 000001 for each clinic, and increase incrementally. - Add a flag before issuing the invoice, if the patient agrees or not to send his invoice to financial authority. The result must be printed on the invoice. - Block the possibility to issue the same invoice more than one time. Once issued an invoice can only be modified, deleted and print. - Add a custom text to the invoices (PRESTAZIONI ESENTI DA IA AI SENSI DELL' ART 10 COMMA 1 N.18 DPR23/10/72 N.633 E SUCCESSIVE MODIFICHE.) - Add on the invoice the payment way (cash, card, etc.) – information stored in the DB - Before issuing the invoice, the user has to be obliged to choose the VAT, otherwise the invoice shouldn’t be issued.