Adiyah, when it comes to content migration, keep these in mind:
- If the content is structured content (e.g. products, news, jobs, etc.) then you can create Page Types in Kentico and use the Import Toolkit Dawid mentioned by map the data fields.
- If the content is unstructured like landing page, then it's better for you to manually bring it over. Also in the process consider how to use Kentico web parts/widgets instead of copy the whole HTML output of the page into Kentico.