How do I protect my projects concept when looking for partners?

I would tell the person in this situation that this is the wrong question.

The right question is, “can I execute this idea better?” Any success will always invite imitation. No competition usually means no profit.

Short answer is you don't. You can always go for an NDA but that's more to make yourself feel better rather than to protect your idea. Best protection is knowing that you can do you can execute your thing better than anyone else ever could.

There is mutual respect but if you are scared you can have then sign an NDA, which is a legally binding contract.

https://www.nolo.com/legal-encyclopedia/sample-confidentiality-agreement-nda-33343.html

Hi Herschel, if you join Audacity.id, the platform acts as a legal container for start ups to build their teams without any risk. It can also help you to raise capital too. Its free to sign up.

no need.. ideas are cheap. execution is where the value is

Can I tell you something from my experience as a developer who gets approached to help build these ideas.
All founders believe their ideas will work, lots believe their ideas will become unicorns.

I don't have enough fingers on my hands to count the times that an idea stage founder has put an NDA in front of m e just to tell me the idea. I'm not joking when I say that every one of those times the idea ended up being underwhelming and all I have left about all these experiences is that I can talk about it.

Reality check. If you are developing some hi-tech quantum computer or the next great battery made from sea water, sure, protect your idea.
But if your idea is the next facebook or airbnb clone, just talk about it with people and a surprising fact to new founders is that all the feedback you get will made your idea stronger.

It is always, 100% of the time better to share your idea with as many people as possible. No one is going to steal your idea, and ideas without execution are worthless. More likely is that you could scream your idea from the mountain tops and struggle to find anyone interested in working with you.

You should get rid of that line of thinking unless you are willing to put serious cash upfront on something that is patentable it's probably not indie than, and it usually doesn't lead to the right path.
This path is mostly good for serial inventor and leasing a patent out.. and works for only a subset of businesses.

If you can't be open about the idea you hinder your own progress mostly.

Are there cases for secrecy, yea they are a few, but very few are really valid