The approach presented here has great potential to study the growth and self-assembly processes on liquid surfaces in soft matter systems such as e.g. colloidal crystals, liquid crystals, Gibbs and Langmuir monolayers, proteins and peptides, electrochemically induced growth of ultra-thin crystalline layers at liquid-liquid interfaces. It can be used as well to analyze deposition of thin films or 2D materials, layer-by-layer self-assembly, and molecule adsorption, not only on liquids but also on solid substrates given that the substrate surface is bent. The work is organized as follows. First, we introduce the principle of the method. Then we demonstrate how the reflection signal on the detector depends on the graphene coverage on the liquid copper substrate. Next, we show that the spatially resolved XRR at a fixed incidence angle can be applied to follow the growth process in real time as an alternative to optical microscopy. At last, we derive the interface parameters of the individual flakes such as their height on the metal substrate by splitting the conventional XRR scan into two components of the covered and non-covered areas.