Hey there, how are you?
I'll be precise, i am an expert WordPress plugin developer, and have worked on various nature of wordpress projects, from corporate websites to wooCommerce based eCommerce websites, as your website is on website plus woocomerce, i have high expertise in that area,
As for payment gateway, i have integrated custom payment gateway before into woocommerce, like Authorize, securepay, etc. so your work will be in experienced hands.
Lets discuss more via chat,
Talha.