Q: Help please :)

you can not access the phone when find my iPhone of its previous owner is turned on. All you can do is to contact he former owner, only him can remove activation lock.

Activation lock cannot be bypassed. You will need the previous owner to remove it if you ever wish to use that iPhone.  Apple will not help you remove activation lock.  It is up to the previous owner to release it.

Find My iPhone Activation Lock - Apple Support

If you are at the activation screen and seeing the requirement to sign in with the AppleID that was used to set up this iPhone, that is activation lock. You cannot bypass activation lock. The previous owner will have to remember or recover the password they used to set it up in order to remove it. There is no other solution for activation lock.

If the previous owner cannot or will not help you, then demand your money back. They should never have sold a device with activation lock still active.

What to do before selling or giving away your iPhone, iPad, or iPod touch - Apple Support

you cannot access the phone, without a right password and user's name of previous owner, this is activation lock, you can access just the set up process