Yes, thanks. I realised that already.
The solution posted by Stone3t was helpfull too.
It is enough just a little open the middle frame at the middle top close to the CMOS battery to disconnect it from the motherboard.
I used a small pincers to disconnect the CMOS battery cable and a needle to connect it to the motherboard.
So, it is not needed to remove the middle frame completelly and also it is not needed to disconnect cables, wifi, ssd etc.