From what I have read you could be stuck in Google sandbox. This takes up-to 6 months to alleviate itself and allow your rankings to flow naturally.
What you could do while you're in this is improve your internal linking strategy and quality of backlinks (So that when you do come out you rank high). For backlinks if you are serious about your website and want it to stay around I would avoid PBN's. What you could do is install the chrome extension 'Check my links' and then go to Google and search Niche + 'Resource Page' or Niche + 'Helpful sites' and other variations. Once you have got a list of these websites that offer resources on use the chrome extension on them looking for dead links. If you get any dead links then try to reproduce the page, and contact the web master notifying them of their dead link and offer your link as an alternative.
For your internal linking methods, I would suggest you produce a lot of content of around 500 words (minimum) all based around the main keyword of your ranking article and link back to that article with different relevant anchor texts. These articles would be more advisable to link to with comments and such than your main ranking page.
If you're struggling for content topics, you could go to youtube and take some relevant videos (look for none-watermarked ones), embed them in your topic and basically cover what gets said in the video. You want to remove the option for showing related videos too. (Well you don't have to, but its just my preference.).