"I have installed my new Intel dual band Wireless AC-7260 but the operation system behaves strangely"
That is the problem. Only integrators and OEMS are allowed to install/upgrade these adaptors.
Review these two links:
This message was posted on behalf of Intel Corporation
To confirm Al Hill's response, Intel does not support wireless integrations by end users. This is because we do not market wireless adapters as retail products. These adapters are only sold to, and often modified specially for each original equipment manufacturer (OEM).
Our recommendation in this case will be to contact your computer manufacturer, and purchase an approved wireless adapter from them. Keep in mind that these products should only be installed by your computer manufacturer or their authorized representative.