as stated by the previous member, landing pages are hard to optimize due to lack of informational content and because they're leaning heavily on sale-trigger type of content (for lack of a better term as English is not my main language either

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This being said, are you talking about REAL landing pages (as in: lead capture pages, salesletters, etc), or are you calling your normal content pages as landing pages? Because, technically, all pages are landing pages since they allow people to... well... land on them
But, if by landing page you mean info pages (ie. pages with informational / educational articles on them), then those are easy to optimize by following a few SEO rules: semantic SEO (using SEO entities and LSI terms), using optimized images and sub-headings, etc...
Anyway, I guess the main starting point in offering advice is by asking what you mean by "landing page". If it's sales-oriented pages then there isn't much you can do I'm afraid (at least not that I know of)... besides maybe having a domain name with really high authority (DR 50 or higher), but even then landing pages don't rank in google anymore like they used to 15+ years ago, so I genuinely don't think there's anything you can do about it besides bringing traffic to them in other ways (Reddit, social media, forums, PPC, etc)