how to optimize seo I have done various methods from entering keywords in the title, description, alt img, file name, html class name and entering keywords in the content is there something missed?

My rich snippet is not showing in search. is there something wrong with my code?

{
  "@context": "https://schema.org/",
  "@type": "Product",
  "name": "Hafiz Laundry Kiloan Satuan Express Terdekat Surabaya Kilat",
  "image": {
    "@type": "ImageObject",
    "url": "https://laundryexpress.web.id/laundry-kiloan-express-terdekat-surabaya/assets/images/bglandry.png"
  },
  "offers": {
    "@type": "Offer",
    "priceCurrency": "IDR",
    "price": "10000",
    "availability": "https://schema.org/InStock",
    "url": "https://laundryexpress.web.id/laundry-kiloan-express-terdekat-surabaya/",
    "priceValidUntil": "2034-12-31T00:00:00.000Z"
  },
  "aggregateRating": {
    "@type": "AggregateRating",
    "ratingValue": "5",
    "ratingCount": "97856",
    "reviewCount": "97856",
    "bestRating": "5",
    "worstRating": "1"
  },
  "description": "Hafiz Laundry Kiloan Satuan Express adalah layanan laundry profesional yang menyediakan solusi terbaik untuk kebutuhan pencucian Anda di Surabaya.",
  "brand": "Laundry",

I always update posts, photos, reviews and everything is guaranteed to be relevant, but why is it down? Is it because the content of my post is not of good quality, it uses more keywords, so there are too many keywords or what? can it be repaired?

I was active at that time but my ranking continued to decline because my GMB posts had a lot of keyword stuffing, in the end I deleted my post, but it never rose in position. I've also updated posts, images, messages, reviews and I've even optimized everything gradually but it hasn't improved. Is there a tool to check the free and paid versions of GMB scores?

Are there any tools to check content quality other than Moz, Semrush, Ahref, Ubersuggest?

I have experienced a decline in my ranking on my Google business profile, from ranking 1-3 dropping to 10+, what is that due to? I previously bought reviews but that was a long time ago and once was just a little bit to look professional. before going down, I made changes and posted a post

how to create a lot of keywords but not detect SEO spam, such as creating 50 keywords repeatedly and the keyword density is not calculated, such as hiding keywords so they don't get crawled, a kind of keyword manipulation that has been written many times but is not detected.

when I checked it turned out to be a duplicate page with "index.html" how do I fix it? so there are no duplicate pages

the content is not created by AI, every time the position rises it won't be crawled for about 3 days in the future then it will fall again, I'm confused about how to solve it, is it because of the 304 cache?

What do you mean by improving quality? I've checked my SEO score, it's already good at 85+. what needs to be improved? Is there a technical problem or something that caused the decline?

I have a website where all the SEO has been optimized, when Google automatically re-crawls it. then my website ranking dropped drastically and it took 7 days to come back and in 10 days it will be re-crawled again then it will go down again, so I can return to the initial position in only 2-3 days, what is the reason for that? even though everything has been optimized, how come every time it is crawled it drops drastically even though there is no penalty or anything like that?