We explore diboson and top quark pair productions in proton-proton collisions at a new centre-of-mass energy, 5 TeV, using 304 $\rm{pb}^{-1}$ of data collected in 2017 by the CMS experiment at the LHC. The diboson, WW, WZ, and ZZ, cross sections are measured analyzing events with two, three or four charged leptons in the final state. The measured cross sections are compared with NNLO predictions and across other experiments. The top quark pair production measurement is performed using events with one electron and one muon of opposite sign, and at least two jets. To reduce the statistical uncertainty, a combination with the result in the l+jets channel, based on 27.4 $\rm{pb}^{-1}$ of data collected in 2015 at the same center-of-mass energy, is then performed.