S7 won't boot: fixed blue LED and blinking green LED

Hi, my S7 had some battery related problem, and in the past some times failed to recognise the real battery level.

Now I have substituted my old battery with a new one and I have the problem explained in the title. When I push the "power on" button, the S7 vibrates and a fixed blue LED + a blinking green LED show up for some seconds, then "menu" and "return" buttons light up and finally all lights disappear and the screen remains black.

The combination "Power button + volume down" gives the same result, and the combination "Power button + home + volume up" gives no result.

If I connect it to a power cord, after some seconds a fixed red LED shows up, then in some minutes it becomes green. Nothing appears on screen and pushing *any* button result in a freeze from which I can exit only disconnecting the battery, during this freeze the phone heats up.

I think the smartphone is failing again in the measuring of the battery level, since it is behaving like the battery is empty. Any idea about how to solve this?