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I think it's a very dangerous idea to migrate your website to another platform on your own. No matter how diligently you do it, you won't be able to maintain your position in the search engines. I say this from personal experience.
It is better to contact the professionals. This team is excellent at helping you migrate your site to WordPress (Heidelberg).

@seotools02 First of all, it is worth analyzing the visibility of your website. To do this, you can use various services, including Moz.
Then you can start optimizing.

• You need to supplement the pages with relevant keywords. True, over time, their relevance decreases, so it is recommended to update the semantic core every six months;
• Write unique meta titles and meta descriptions;
• Work on the web design and page structure, if necessary, add blocks with photos, videos, etc.
• Optimize site speed. To do this, you can reduce the size of the images.

You can analyze the website speed using these services: Pingdom, Google PageSpeed insights, WebPageTest. I would also advise optimizing images. It is better to publish photos in JPEG format, it allows you to compress images without losing quality.