Murcielago relay in fire

Hi everyone,

From some weeks my Murcielago 2006

it's hard to start after two days, the voltage is around 11 before ignition and it's difficult to start, once the engine has started it's around 13.2-4

The other day in traffic at low engine speed the gearbox light came on and the car from N no longer went into 1st gear, then I let it rest for a few minutes and the gearbox worked again. after a few days on the highway I put the car in neutral in traffic and the car no longer went in 1st gear! (that morning before starting the voltage was 8). after the car stopped on the motorway I had to tow it, the car no longer started even when I connected it to an external cable. the mechanic changed the battery (it was from 2019 and apparently died. The car is still at the mechanic's, today he turned it on to do further checks, as soon as it was turned on, the car started to smell burning, from behind the driver's seat where the fuses are. Result: melted fuse, it melted and doing a test it makes sparks and fire . What do you think it could be? I'm worried . the fuse corresponds to the “secondary air pump “ ?

this is the video and attach one photo find in the forum from a car ( not damage )

 

thank you