Hello vipmast!
First of all please share or send me your website link. I can sort out why os-cart checkout procedure is slow. I am expert in HTML/CSS, PHP etc, So creating a contact form is easy job for me. Please before go ahead I want to visit your website first. I assure you, I will provide you 100% result with in concern time. Waiting for response. You must reply for getting solution of your problem. Thanks
Best Regards