Configure Presta Or Like Shopping Cart, Write pHp Captha for contact and resellerlogin with existing quick cms site

I have already an existing site. I made it in parts. Now I want to use a better shopping cart( like Presta or OpenCart )and use the link in the existing site. You are more than welcome to suggest Economical reasonable improvements in my existing site. NB:No Half Experience people ( No Self Praises please i am allergic to them ( millions in India ) , No CMSitis,WPitis sufferers, Serious experienced designers or developers) and no exorbitant unrealistic [login to view URL] is not a difficult job.