Diffusive shock acceleration in supernovae can accelerate particles to very-high energies (VHE, E > 100 GeV). HB3 is a supernova remnant (SNR) detected by the Fermi Large Area Telescope in 2016 with 6 years of data, adjacent to the south-eastern part of the giant HII complex W3. The low energy gamma-ray emission of both systems shows a clear signature of proton acceleration. Here we use a significantly larger dataset of 14 years of data with the improved P8R3 instrument response functions to perform a precise morphological study of the SNR and W3 above 1 GeV using multi-wavelength data in the X-ray and radio bands. This allows us to derive the spectra of both systems above 100 MeV. In this presentation, we will review the consequences of this precise analysis providing new constraints on the acceleration and propagation of cosmic rays in this region.