Regaining Keywords Rank (SEO)

I have a website with a landing page that was optimized for 2 keywords in 2013 in Cairo, Egypt. The website remained on page 1 for 5 years on Google since the SEO done was all Organic. In 2018, another SEO specialist used Black Hat SEO without my knowledge to achieve rank for another keyword for an internal page of the website. The website then rapidly lost rank for the initial two keywords and the last one too. I want to regain the rank for the first 2 keywords using only organic, White Hat SEO techniques and KEEP the RANK.