You can likely find some experienced/proven freelancers on this site if you post an entry in the classifieds. Given the phrasing of the question, I'm assuming you have the capital to finance such outsourcing. https://www.gamedev.net/forums/forum/29-hobby-project-classifieds/

Insofar as partnering with a publisher, or development house, we're talking some serious muscle, or capital, and/or the right prototypes/ideas (which you may have, don't know). In such a case I wouldn't be of much help  

You ask about "good development companies", and "a quality project", but then post in For Beginners rather than the business area of the site.  Good companies that make quality 3D games come with a price tag.

I know several good contracting companies, but unless you're talking about million dollar projects with payments at regular milestones, they won't be interested.

I know a few mediocre contracting companies, but I doubt they'd be interested in anything under a quarter million, although if it is a small product and closer to $100K, they might still be interested.

Good contracting work has a price tag. Currently, I estimate with $15K per work month for good work, $10K per work month for so-so work.

If you are talking about this kind of project and will send me a direct message with additional information so I can vet both you and the project so I don't look bad, I can get you the bizdev contacts.

On 1/18/2019 at 10:23 PM, Sharik said:

I really need an experienced game development company to help me with my project that is getting a bit too long to make. Please tell me which companies were the easiest for you to work with ?

Hi, could you describe in more detail what you want?  Do you want to hire a team or do you want to join the team?

Thank you

8 hours ago, Sharik said:

I have an idea and I would like to discuss its implementation, at least at least its possibility!

There are several different groups to talk to about a pitch like that.

Talk to the developer if you have money to fund your product.  If you don't have the money to develop the product, a developer will not be interested.  Usually the first payment is due when the contract is signed, and other payments follow on a monthly milestone basis.

As mentioned above, I'm one of many people on the forums who can help you find good contacts if you have at least five digit funding lined up.  Few companies are interested for less than $100K, but some individual contractors may be interested as long as you have money up front.

Don't have money? That's a problem.

Talk to a publisher if you want them to fund a project idea. Understand that nearly every submission gets declined. Consider the parallels in the book world: Harry Potter was rejected by 12 publishers before being accepted, Dune was rejected by 20, Asimov was rejected over 60 times, John Grisham was rejected 16 times. The book Chicken Soup for the Soul, now a best-selling series, was rejected 144 times before finally getting accepted by a publisher. Those were all products that were basically complete BEFORE looking for funding.  If you think those are bad for high-grossing best-selling books, know that games ideas have an even worse acceptance rate by publishers.  Be prepared with a working demo, because nobody will buy your idea by itself.

Tom has written about it many times, leading off with this article. Nobody will buy your idea. If your idea is amazingly good there is a minuscule chance that somebody will help fund development where you're still doing the work, but expect them to take most of the money since they also took all the financial risk. The deals depend on a bunch of factors, but as a no-name developer if your idea was accepted you might get 8% of net revenues if you get a good contract, perhaps 15% or even more if you have a big name and a record of success, less if you have a risky product or bad contract. (That's before even getting in to Hollywood Accounting and how some publishers find ways to never make any net revenue.)   If you want an advance on royalties to help pay for a roof and food during development, you may get even less because you're asking them to take even bigger financial risks.