I have a friend who works for a company, the company’s website has been created using HTML and Bootstrap, and they want me to migrate their website to WordPress (without affecting the SEO and the Ad Campaigns). I’ve told them that that doesn’t seem to be possible because the best option is to redesign and rebuild the website on WordPress while keeping the same permalinks, post/media names to keep the SEO.
They’re not rebuilding it (on WordPress) because they’ve spent some money on the ad-campaigns and want to keep the ad campaigns. And also because they’re a bit familar with WordPress.
Is there anyway to migrate/integrate their website on WordPress?
Any help would be appreciated. Thanks!

No, there’s no migration from html to WordPress. It’s a rebuild. Given that the current site is html I wouldn’t imagine it’d be difficult.
You can only re-build it within WordPress, there’s no specific migration for this.