We theoretically describe the stationary regime and coherent dynamics of a capacitively shunted transmon-type qubit which is placed in front of a mirror. The considered qubit is irradiated by two signals: pump (dressing) and probe. By changing amplitudes and frequencies of these signals we study the system behaviour. The main tool of our theoretical analysis is solving of the Lindblad equation. We also consider Lindblad superoperators in charge and energy bases and compare the results. Theoretically obtained occupation probability is related to the experimentally measured value. This study helps to understand better the properties of qubit-mirror system and gives new insights about the underlying physical processes.