Hi everyone, i have  a business and want to protect it with a powerfull spell, as well as inhibiting people to steal from me. The only thing worrying me, is that i do not want to alter anyone's life or influence it negatively, even if this person would steal from me,

Blessed be

That's great you have asked that Payewacker!

I will answer for all Faiths. Whether you be Wiccan,Christian,Buddhist or other respectable system of belief.

The greatest spell/protection you can have against thieves is your conviction that whatever Good that comes to you , nobody else wants that.

If you know that, you are automatically protected against many things.

I made a post in the "Psychic" forum titled "NOBODY ELSE CAN TAKE YOUR (GOD-GIVEN) RIGHT IN LIFE" It might be helpful for you to read that as it will free you from many misunderstandings concerning that subject...well provided you are open to the ideas in the text.
The same goes for anybody reading this

If you want to protect whatever you have, the first step is to know unwaveringly that it is Divinely protected. You talked about spells Payewacker, then vizualize also your business being constantly protected by an image of your choice that raise that awareness of the Divine protection.

Do that daily and it will help.

Now , we know that if you really believe  and really convinced that your Good is protected  by the Divine , nobody else can...

To believe the opposite is really deny the power of the Divine.If nobody else can, then it means that whatever others negatively try to do will eventually fail, whether you are aware of it or not.

Now , you can make some affirmations for yourself from what I have just said.

Furthermore, as you probably know, the best spells are self-made.

Below are hints:

With essences and herbs

-You can burn Sage, Agrimony and Hyssop while doing your Prayers and some places in your Business

With Crystals

-Black Tourmaline, Amber,Citrine to name a few

With Business

Learn more about the natural laws of Business too : "the 100 unbreakable laws of Business" by Brian Tracy might help . All books by Robert Kiyosaki
"How to attract Success" by F. W. Sear

No matter what spells you make, if you don't know nothing about the Businesss world, you will eventually fall

Get busy developping a "Prosperity Consciousness" and you won't need to deal with so-called "thieves"

Wishing you the best!