I’m working on setting up an online store using OpenCart and would like to integrate payment gateways such as PayPal, Stripe, or Razorpay to allow my customers to pay securely. I’m fairly new to OpenCart and not sure where to start. Here are a few things I’m hoping to understand: 1.Which payment gateways are easiest to integrate with OpenCart? 2.Do I need to install any extensions or modules to get started? 3.Are there any free modules available, or do I need to purchase one?