1.You have to build your MVC project and copy the resulted .DLL file into the bin directory of your application deployed location (on your server). (If you change only the view, in that case you should copy the view file in the associated folder location on your server in View sub-folder.)
2.Regarding your problem root related with Paypal, you should put all your PayPal settings, including the return URL as application settings into the
web.config
file like in the next example.
<appsettings>
<add key="webpages:Version" value="1.0.0.0" />
<add key="ClientValidationEnabled" value="true" />
<add key="UnobtrusiveJavaScriptEnabled" value="true" />
<add key="PayPalUsingSandbox" value="true" />
<add key="PayPalSellerID" value="XXXXXXXXXXXXX" />
<add key="PayPalCancelUrl" value="http://localhost:62710/Order/CancelFromPayPal" />
<add key="PayPalReturnUrl" value="http://localhost:62710/Order/ReturnFromPayPal" />
<add key="PayPalNotifyUrl" value="http://localhost:62710/Order/NotifyFromPayPal" />
</appsettings>
3.Better is to use multiple config files, so for example your could have one config file for debug (your testing server) and a 2nd one for release (the real server), and each of them to have different Paypal settings. See details about multiple config file in the next links:
ASP.NET MVC: Keep Private Settings Out of Source Control[
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http://deanhume.com/home/blogpost/working-with-multiple-web-config-files/4100[
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