PHP script for a Cyprus Rent-A-Car Company

I need help to complete my project , I may pay a max of $200.00 for this help(total) .
I make a PHP script for a Cyprus Rent-A-Car Company but has some problems(my first long project in PHP):

1) else-if iteration make wrong decisions where is the mistake ?
2) Transfer variables to a web form(from prior webpage) and then submit them to an html file/email address ?
3) In PHP a URL like :
http://www.fff.com/next.php?id=xx
(xx in this example may be a variable: $xx, if yes is written samely ?) work ? To next.php to get this variable value a statement like:
<?php echo $_GET['id'];?> is correct ?????
4) After these, may ask some other small questions ... !
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The Script start at(web form):
http://paphoscarhire.com/php/a1.php
go to(decision php script):
http://paphoscarhire.com/php/b1.php
after to(correct decision):
http://paphoscarhire.com/php/normaldays.php
and finally to (booknow.php) :
http://paphoscarhire.com/php/booknow.php
booknow.php submits web form to an html webpage & to an email address.
This project will make an Instant Quote Calculation for car rentals like the www.cyprus-car.com .