Hello,
After reading your job description, I guess you either have an old theme which you should get rid of and build something new that supports all devices and it looks elegant!
Or, it is a new theme that looks good but - unfortunately - the original developers didn't make it responsive which is really crazy, as they should have done this before delivering the final project.
Anyhow, I got your back.
I will check your current theme's look, performance, and finally the code scheme and documentation, then we will determine the best decision to take to your theme.
*The price might vary, according to our decision, I will provide you with the estimated working hours.
Hope to start working with you.
Best Regards,
Yahya Elharony