so I am looking for a way to calculate and show dynamically as text the x-Axis-value of the Intercept of those two curves.

    Manipulate[Plot[s*(1 + r/12)^(y) + m*((1 + r/12)^y - 1)/(r/12), {y, 1, 36},
    GridLines -> {None, {g}}, PlotRange -> {0, g*1.1}, 
    GridLinesStyle -> Directive[Red, Thick], 
    AxesLabel -> {"Months", "Fr"}, 
    PlotLabel -> "Saving Calculator"], 
    {{s, 100, "Inintial Savings"}, 0,   10000, 100, Appearance -> "Labeled"},
    {{r, 0.05, "Interest Rate"}, 0, 0.1, 0.01, Appearance -> "Labeled"}, 
    {{m, 50, "Monthly Savings"}, 0, 500, 10, Appearance -> "Labeled"},
    {{g, 5000, "Saving Goal"}, 1000, 100000, 1000, Appearance -> "Labeled"}]

Any help would be much appreciated!
Its about the intercept of the red to the blue curve.