Since this is about [ErbSt/SchenkSt], the corresponding Purple Book (Valuation Act) applies.
Real estate. The whole thing is either done using a cost approach or the income approach. What matters here is the type of property or building. With the information provided, one would have to speculate on what exactly is involved.
I assume here a single-family house or a two-family house, for which the income approach would then apply. Since only you have all the information necessary for the valuation according to paragraphs 78 to 82 BewG, I recommend taking a look at the law; then you will know which value the tax office assumes for a potential gift/inheritance tax.
You always have the option to challenge this value through a separately commissioned appraisal, see Par 198 BewG.