  Magnetar hyperflares are the most plausible explanation for fast radio bursts
(FRB) -- enigmatic powerful radio pulses with durations of several milliseconds
and high brightness temperatures. The first observational evidence for this
scenario was obtained in 2020 April when a FRB was detected from the direction
of the Galactic magnetar and soft gamma-ray repeater SGR\,1935+2154. The FRB
was preceded by two gamma-ray outburst alerts by the BAT instrument aboard the
Swift satellite, which triggered follow-up observations by the High Energy
Stereoscopic System (H.E.S.S.). H.E.S.S. has observed SGR\,1935+2154 for 2 hr
on 2020 April 28. The observations are coincident with X-ray bursts from the
magnetar detected by INTEGRAL and Fermi-GBM, thus providing the first very high
energy (VHE) gamma-ray observations of a magnetar in a flaring state.
High-quality data acquired during these follow-up observations allow us to
perform a search for short-time transients. No significant signal at energies
$E>0.6$~TeV is found and upper limits on the persistent and transient emission
are derived. We here present the analysis of these observations and discuss the
obtained results and prospects of the H.E.S.S. follow-up program for soft
gamma-ray repeaters.
