Even I am not
seo expert at all I can tell that there is a lot of things on this website you can improve. For the beginning you don't have keyword and description meta tags.
Than You have much too much unnecessary java script and css code in your head sections that you can have in separate external files.
I did not see any H1, H2 .... tags on your source code.
This is just a couple of simple things you can change on that site for the beginning.
Other thing you can consider is to explain to your client to hire professional
SEO Company.