To my knowledge this isn't allowed but times may have changed since I was a moderator.

so we give you GP and get only 10% of the winnings if there is any?

Yeah this is %100 against the rules. I would recommend you to take this down.

Why is this better than staking on my own section:

1) You're not giving them 50/50 odds as implied as you're taking a 10% cut. 

2)  Generally the outcome for someone who continuously gambles with 50/50 odds, even more so for 40/60 odds like this is.

3) This is irrelevant and pure luck based as you previously stated (50/50 odds) even more so after taking 10% commission, the only thing you can guarantee is to not missclick/make noob staking mistakes HOWEVER the customer has no proof of this as you don't appear to stream or record stakes.