SEO Help Required for My Website

[JonathanNaylor]

Hi,
I have a website theacademicpapers.co.uk which was on top positions till last year. However, after last year's Google Update in July/August, its ranking was down. Later after a months, its ranking started again to boost but after a few days it was down again. 1 Month ago, its some keywords again appeared on 1st page of Google but just after a few days, we lost ranking. I am currently following these strategies
1. Guest Posting
2. Contextual Linkbuilding
3. Forum Posts/Comments
4. Questions/Answers
5. PPT/Video/Infographics Sharing

I have updated content also but it does not have any effect. I have Disawwowed Spammy Backlinsk but result remained same. Can you please suggest any solution which I should adopt? I doubt that there is something in website which I am unable to find. Technically, we are using .php extension at end of permalinks. Further, we have implemented Lazyloading at the website. Currently, the most effected page is this one theacademicpapers.co.uk/dissertation-writing-services-uk.php

I am waiting for a solution/suggestion from you guys to improve the ranking again.