Narrow-Line Seyfert 1 (NLS1) galaxies exhibit narrow permitted Hβ lines (FWHM < 2000 km/s) and strong Fe II multiplets with low black hole (BH) masses (< 10⁸M⊙) and high Eddington ratios. The BH masses and predominantly disk-like hosts suggest that NLS1s are early-stage Active Galactic Nuclei (AGN). They host the lowest-mass super-massive BHs that can launch relativistic jets and offer insights into the conditions necessary for jet formation. Available optical spectral catalogues have low S/N ratios, and classifying NLS1s using them is challenging. Using FORS2 observations of ~100 candidate NLS1s, we aim to classify the sources and perform detailed spectral modelling of Hβ, [OIII], and the Fe II pseudo-continuum using Gaussian, Lorentzian and Voigt profiles. Based on preliminary results, we found 16 changing-look AGN and a contamination fraction of ~28% in our data. We study how, in NLS1s, the broad Hβ line profile transitions from a Lorentzian to a Keplerian motion-dominated Gaussian with increasing BH mass, to determine whether this change is an essential part of intraclass evolution. By modelling the lines with Voigt profiles, we test whether the sources previously best described by Lorentzian or Gaussian functions are dominated by the turbulent or Keplerian component, respectively. In this talk, I will present the spectral analysis of NLS1s and changing-look AGN and discuss our findings and future plans.