This work of thesis is devoted to the study of the blazar S5 0716+714, with data taken in the very-high-energy (VHE, E>100GeV) γ-ray range and in the optical band from 05 Dec 2015 to 12 Mar 2021. The data have been acquired during a multiyear campaign led by MAGIC (Major Atmospheric Gamma-ray Cherenkov telescopes) and active for three consequent observational cycles. S5 0716+714 is a well known blazar, categorised as a BL Lac type object. It is particularly famous for its variability in many energy bands. During an impressive flaring activity in 2015, the source reached the historical maximum in the optical band. In that occasion, a very fast rotation of the EVPA (Electric Vector Polarization Angle) was reported. EVPA rotation were observed in several occasion happening during a flaring state with γ-ray emission: so a monitoring of S5 0716+714 was organized by MAGIC together with optical telescopes in the network WEBT (Whole Earth Blazar Telescope) and within the BU (Boston University) VLBA-BU Blazar Monitoring Program. The goal of my thesis is to prepare the VHE γ-ray dataset obtained with the S5 0716+714 monitoring so far and search for correlation between the optical and optical polarization data that were taken simultaneously to MAGIC. In this work of thesis, four observational periods of MAGIC data about S5 0716+714 have been analyzed. From my analysis, a low state of the source has been identified together with a very bright flaring state in 28-29 December 2017. Another interesting period was ST0312 where another flare activity (14 Feb 2020) was spotted in VHE γ-ray range.