A fill level measuring device for mounting in a dome-shaft , which is arranged in a vertex area of a container , and for determining a position of a fill level (d L ) of a filling material and/or of a separating layer (d L ) between two filling materials in the container , wherein the fill level measuring device is configured to emit electromagnetic or acoustical waves towards a filling material surface, the fill level measuring device comprising: an echo-curve acquisition device for capturing at least one echo-curve; an echo-curve identification device for evaluating the at least one echo-curve; a tracking device for grouping echoes from various measurement cycles in a way, that echoes, which are caused by the same reflection spot in the container and that emerge from the same signal paths, are combined to tracks; and a multiple-echo detection device for classifying at least one first echo (515, 610, E MLN1 ) as a multiple echo of a filling material reflection and of a second echo (515, 611, E MLN2 ) as a multiple echo; characterized in that the fill level measuring device further has a self-learn device , which is designed for automatically determining a dome-shaft length d D of the dome-shaft by using the first echo (515, 610, E MLN1 ) classified by the multiple-echo detection device , which has a first electrical distance (D MN1 ), and the second echo (515, 611, E MLN2 ), which has a second electrical distance (D MN2 ), wherein the self-learn device is configured to infer the dome-shaft length d D according to this formula: d D = N 1 + 1 ⋅ D MN 2 − N 2 + 1 ⋅ D MN 1 ε L ⋅ μ L ⋅ N 1 − N 2 , wherein N 1 defines the order of the multiple echo at the first electrical distance D MN1 , N 2 defines the order of the multiple echo at the second electrical distance D MN2 , and ε L describes the relative permittivity and μ L describes the relative permeability of an overlay medium. an echo-curve acquisition device for capturing at least one echo-curve; an echo-curve identification device for evaluating the at least one echo-curve; a tracking device for grouping echoes from various measurement cycles in a way, that echoes, which are caused by the same reflection spot in the container and that emerge from the same signal paths, are combined to tracks; and a multiple-echo detection device for classifying at least one first echo (515, 610, E MLN1 ) as a multiple echo of a filling material reflection and of a second echo (515, 611, E MLN2 ) as a multiple echo; characterized in that the fill level measuring device further has a self-learn device , which is designed for automatically determining a dome-shaft length d D of the dome-shaft by using the first echo (515, 610, E MLN1 ) classified by the multiple-echo detection device , which has a first electrical distance (D MN1 ), and the second echo (515, 611, E MLN2 ), which has a second electrical distance (D MN2 ), wherein the self-learn device is configured to infer the dome-shaft length d D according to this formula: d D = N 1 + 1 ⋅ D MN 2 − N 2 + 1 ⋅ D MN 1 ε L ⋅ μ L ⋅ N 1 − N 2 , wherein N 1 defines the order of the multiple echo at the first electrical distance D MN1 , N 2 defines the order of the multiple echo at the second electrical distance D MN2 , and ε L describes the relative permittivity and μ L describes the relative permeability of an overlay medium. <EOS>