  Our aim is to examine the size, kinematics, and geometry of the broad-line
region (BLR) in the double-lensed quasar Q 0957+561 by analyzing the impact of
microlensing on various rest-frame ultraviolet broad-emission lines (BELs). We
explore the influence of intrinsic variability and microlensing on the C IV, C
III], and Mg II emission lines through multiple spectroscopic observations
taken between April 1999 and January 2017. By utilizing the line cores as a
reference for no microlensing and correcting for the long time delay between
the images, we estimate the sizes of the regions emitting the broad-line wings
using a Bayesian approach. Our study of the microlensing amplitudes between the
lensed images of the quasar Q 0957+561 reveals differing sizes of the regions
emitting the three prominent BELs C IV, C III], and Mg II. The strength of the
differential microlensing indicates that the high-ionization line C IV arises
from a compact inner region of the BLR with a half-light radius of $R_{1/2}
\gtrsim 16.0$ lt-days, which represents a lower limit on the overall size of
the BLR and is comparable to the size of the region emitting the r-band
continuum in this system. A somewhat larger size of $R_{1/2}\gtrsim 44$ lt-days
is obtained for the semi-forbidden line C III]. Microlensing has a weak impact
on the lower-ionization line Mg II, which is emitted from a region with a
half-light radius of $R_{1/2} \gtrsim 50$ lt-days. These findings suggest that
the BEL regions may have distinct geometries and kinematics, with the more
extended ones being spherically symmetric, and the most compact ones being
nonspherical, with motions likely confined to a plane.
