  The field of exo-atmospheric characterisation is progressing at an
extraordinary pace. Atmospheric observations are now available for tens of
exoplanets, mainly hot and warm inflated gas giants, and new molecular species
continue to be detected revealing a richer atmospheric composition than
previously expected. Thanks to its warm equilibrium temperature (963$\pm$18~K)
and low-density (0.219$\pm$0.031~g cm$^{-3}$), the close-in gas giant WASP-69b
represents a golden target for atmospheric characterization. With the aim of
searching for molecules in the atmosphere of WASP-69b and investigating its
properties, we performed high-resolution transmission spectroscopy with the
GIANO-B near-infrared spectrograph at the Telescopio Nazionale Galileo. We
observed three transit events of WASP-69b. During a transit, the planetary
lines are Doppler-shifted due to the large change in the planet's radial
velocity, allowing us to separate the planetary signal from the
quasi-stationary telluric and stellar spectrum. Considering the three nights
together, we report the detection of CH$_4$, NH$_3$, CO, C$_2$H$_2$, and
H$_2$O, at more than $3.3\sigma$ level. We did not identify the presence of HCN
and CO$_2$ with confidence level higher than 3$\sigma$. This is the first time
that five molecules are simultaneously detected in the atmosphere of a warm
giant planet. These results suggest that the atmosphere of WASP-69b is possibly
carbon-rich and characterised by the presence of disequilibrium chemistry.
