programmer for opencart eshops

i am looking for programmer to knows absolutely the opencart and to have knowledge for server.i need a programmer to support my business the time that i need him.sometimes i need to add categories on site,to change prices banners and sliders.Other times i need to make some modules or to buy modules from platform and setting up for having better business experience my clients.I will not have every month,i calculate that i will need his 5 by 30 hours the month and i will pay him for his support every month either i have job for him either not.I want someboty to be responsible,to have knowlede and give me new ideas to do stronger my eshops.