  Thanks to the advances in modern instrumentation we have learned about many
exoplanets that span a wide range of masses and composition. Studying their
atmospheres provides insight into planetary origin, evolution, dynamics, and
habitability. Present and future observing facilities will address these
important topics in great detail by using more precise observations,
high-resolution spectroscopy, and improved analysis methods. We investigate the
feasibility of retrieving the vertical temperature distribution and molecular
number densities from expected exoplanet spectra in the near-infrared. We use
the test case of the CRIRES+, instrument at the Very Large Telescope which will
operate in the near-infrared between 1 and 5 micron and resolving powers of
R=100000 and R=50000. We also determine the optimal wavelength coverage and
observational strategies for increasing accuracy in the retrievals. We used the
optimal estimation approach to retrieve the atmospheric parameters from the
simulated emission observations of the hot Jupiter HD~189733b. The radiative
transfer forward model is calculated using a public version of the tauREx
software package. Our simulations show that we can retrieve accurate
temperature distribution in a very wide range of atmospheric pressures between
1 bar and $10^{-6}$ bar depending on the chosen spectral region. Retrieving
molecular mixing ratios is very challenging, but a simultaneous observations in
two separate infrared regions around 1.6 micron and 2.3 micron helps to obtain
accurate estimates; the exoplanetary spectra must be of relatively high
signal-to-noise ratio S/N>10, while the temperature can already be derived
accurately with the lowest value that we considered in this study (S/N=5).
