Magento to fix issue on site

Hi, I am looking for Magento experience developer, below is my requirement. My opencart loaded things instantly. And add to cart takes ip to 10 seconds and checkout process is horribly long. Also the images need to Load https when site is accessed via https. Stockinthechannel addon puts them in . Basically if site http load images link http and if ssl load https. The images server has an ssl certificate so just needs to call them https. Thanks