  Observations of the rest-frame UV emission of high-redshift galaxies suggest
that the early stages of galaxy formation involve disturbed structures. Imaging
the cold interstellar medium can provide a unique view of the kinematics
associated with the assembly of galaxies. In this paper, we analyzed the
spatial distribution and kinematics of the cold ionized gas of the normal
star-forming galaxy COS-2987030247 at z = 6.8076, based on new high-resolution
observations of the [C II] 158um line emission obtained with the Atacama Large
Millimeter/submillimeter Array. These observations allowed us to compare the
spatial distribution and extension of the [C II] and rest-frame UV emission,
model the [C II] line data-cube using 3DBarolo, and measure the [C II]
luminosity and star formation rate (SFR) surface densities in the galaxy
subregions. The system is found to be composed of a main central source, a
fainter north extension, and candidate [C II] companions located 10-kpc away.
We find similar rest-frame UV and [C II] spatial distributions, suggesting that
the [C II] emission emerges from the star-forming regions. The agreement
between the UV and [C II] surface brightness radial profiles rules out diffuse,
extended [C II] emission in the main galaxy component. The [C II] velocity map
reveals a velocity gradient in the north-south direction suggesting ordered
motion, as commonly found in rotating-disk galaxies. But higher-resolution
observations would be needed to rule out a compact merger scenario. Our model
indicates a low average velocity dispersion, $\sigma$ < 30 km s$^{-1}$. This
result implies a dispersion lower than the expected value from observations and
semi-analytic models of high redshift galaxies. We argue that COS-2987030247 is
a candidate rotating disk experiencing a short period of stability which will
be possibly perturbed at later times by accreting sources.
