  We study the vacuum properties of the pseudoscalar glueball and charmed
mesons by using the so-called extended Linear Sigma Model (eLSM). This model
includes scalar and pseudoscalar mesons, as well as vector and axial-vector
mesons. We calculate the mesonic and baryonic decays of the pseudoscalar
glueball, where we fixed its mass to $2.6$ GeV, as predicted by lattice-QCD
simulations, and take a closer look at the scalar-isoscalar decay channel. As a
second step, we enlarge the so-called extended linear Sigma model (eLSM) by
including the charm quark to a global $U(4)_r\times U(4)_l$ chiral symmetry.
Most of the parameters of the model have been determined in a previous work by
fitting hadron properties involving three quark flavours. Only three new
parameters, all related to the current charm quark mass, appear when
introducing charmed mesons. We compute charmed mesons masses, weak decay
constants, and strong decay widths of (open and hidden) charmed mesons.
Moreover, we calculate the decay width of a pseudoscalar ground state
charmonium $\eta_c$ into a pseudoscalar glueball and the decay widths of a
scalar charmonium $\chi_{c0}$ into the scalar glueball.
