Everybody who runs a websites gets emails, continuously, from greedy scam artists who claim to “have found errors in your website” or that your website “doesn't rank well in Google,” and they can do something to help you.
It's all a complete lie. Everyone gets the same message, all worded very similarly. They haven't checked your website, at all. Your website could be absolutely flawless, and they'll still say that they found errors. Your website could be the top return for a Google search, and they'll say that it doesn't rank well.
They contact you unsolicited, and claim it's not spam (that's the very definition of spam). They use methods that try to get past your anti-spam filtering. They use faked “from” email addresses wanting to reply back to them at another email address, they're the hallmarks of a con artist. They've proved they're untrustworthy by their very first action. They don't give a damn about you, they're just after your money.
If you're foolish enough to give them money, the chances are that they'll just run away with it. Or worse, if you stupidly gave them your credit card details, they'll steal as much as they can from your account. Harsh words, sure, but people do dumb things all the time, and I want to hammer home that they are very dumb things to do.
You don't need someone else to optimise your website so that search engines find it, you can do that yourself. Just write it well, in the first place: Write naturally, use the proper terms that describe your service, and the words people are likely to use to look for it. Never have “click here” links, always have the link say what it's for. Have your location in your contact details, give some scope to your service area (local-only, state-wide, etc). Smart search engines can extrapolate areas near you from your postal code, when people search for businesses near them (yes, people do that, they prefer dealing with locals, you stand a good chance of getting a good ranking as a local supplier, but the whole world's your competition if you want to be globally number one). Never spruik a hard-sell like a shonky used car dealer. And if you do need professional help, look for someone to help you, don't respond to spam email, they're all scammers. Ask your hosting service to recommend someone if you can't figure out who's genuine and who's fake.
The same advice applies to websites that aren't a service. You don't have to be a shop, you use the same techniques whatever your site is for. Make your site self-explanatory to people who know about whatever your site is for, and to everyone else that doesn't. It's as simple as that.
Doing stupid SEO things actually harms your website, and search engines will downgrade your listings if they discover you trying to game the system. Stupid things like paying for your site to get listed in known shill sites, stuffing keywords into your pages, and using bogus things to lure visitors to your site under false pretences. When you do things like that, you become a scam artist, and bad karma will get you.
I've got into the top of the returned links on Google searches when I've written my pages properly. I didn't even have to pay Google to run an advert. Paid adverts are a scam in themselves, they can cost you a fortune. And when people searching for something see paid adverts, they're often not the best results for them, but the ones that paid for the privilege.
The only (slightly) hard part is getting noticed by a search engine in the first place. Again, don't use a scam artist. Go straight to a search engine like Google, and find out how they recommend you get into their database. Read their own information, not someone else's info about how to do it. But if your website exists, and is mentioned by another website that Google regularly indexes (and it always revisits sites that it's already indexed), Google will find you. Just be subtle and sensible about it.
If you have a Facebook page, make sure your website is part of your user details. If you have a Google account, make sure your website is part of its user details. If you don't have a Google account, set one up. The same goes for just one or two other search engines, look into the ones you might use, ignore the rest. Once you're indexed by one search engine, other ones will find you by themselves. So you really only have to deliberately try to get on the biggest one, Google.
Today (October 2022) this link on Google, itself, is the beginning of all you need to know to get listed by them, read it and look through its links, and hit delete on every spam email that claims they'll help your website: