website visitors down

I am a freelance programmer
same as most people here
but currently I'm studying
SEO is enough to make me dizzy
due to lower customer on my website
do you know what is causing my website down?
some time ago my website occupies
The first rank in the google website
by keyword
Jasa Pembuatan Website
Jasa Pembuatan Software
Jasa IT Development
then now dropped away to page 10
I'm pretty far behind on google search algorithm
data structure?

See original post by jancok13