Hello my friends

I have run to a problem recently and I really don't know how to solve it. some of pages are disappeared from google. At first, they were doing well and it was in the third pages. but now no matter I change the keyword or create a whole new page, Google won't show it. the keyword is powerpoint presentation services, or powerpoint presentation help.

http://assignment.one

I should say I have many pages on the first page and they are fine. 

My guess is that I've got backlinks with the same anchor text. I disavowed all of these links, but still no change.

Can anybody tell me what's going on and how I could solve the problem? Has google penalized me? how can I found out?

Thank you all