Hi,
1. There are many things which happens at that moment:
- the cart is converted into an order and saved in the database. This can't be shortened
- mass actions with "before an order is created" and "after an order is created" are triggered. Based on what mass actions you've configured, it's possible a massaction would take a lot of time to process
- plugins implementing the onBeforeOrderCreate and onAfterOrderCreate are triggered. Some plugins can potentially slow down the process a lot. For example, a plugin integrating with an ERP and having to perform several operations onto the ERP's API to register the order can incure a substantial delay and you can't do much about it
- HikaShop sends the "order creation notification" email to the customer and the "order admin notification" email to the shop owner. Sending an email can take a lot of time, especially if there are attachments. These emails can be deactivated in System>Emails if you don't need them.
- the payment plugin talks with the payment gateway to generate the redirection URL to the payment gateway page. It can take a while based on the distance between your website server and the payment gateway's. It can't be shortened
- the brower retrieves the HTML and then redirects to the payment gateway page. The payment gateway can sometimes process a lot of things on their end at that point which can also lead to delays and you can't shorten it.
2. I'll let TsukiDev, the developer of the plugin, answer you on this as I don't know how the payment plugin works.