Active Galactic Nuclei (AGN) are, in general, described by a spectral energy distribution (SED) consisting of two humps. Extreme Highenergy BL Lac objects (EHBL) are a class of AGN in which the second peak of the SED is located at remarkably high energies with respect to "standard" BL Lac objects. So far, very few EHBLs have been detected in very high energy (VHE) and this thesis aims to investigate their behaviour by analysing data from a particular source. Using recent and unpublished data from the MAGIC telescopes, the high-energy hump of the SED was studied for the EHBL 1E S2344+51.4, a source remarkable because of its intermittent nature. It can show extreme features only temporarily, challenging the understanding of the emission mechanism. 1ES 2344+51.4 was studied in the VHE -ray band for 4 nights in August 2019. 2.74 h of data were collected and analysed, finally obtaining the differential energy spectra and the SEDs for 3 separate nights of observation. The analysis results, compared to results found in literature, help to characterize the source in an enhanced flux state in VHE -ray and add information on the evolution of the hardness of the spectrum in connection with the flux state. This work provides the basis for a possible future study of the intermittent nature of 1ES 2344+51.4.