Below I also posted the code from the DialogApp to better understand. Of course the way it's working right now is that both the DialogApp and my function take the default values I defined as 1 and 0 and run with that, without any influnence from the spinner of the DialogApp. I'm aware, there might be more than one problem with it. But what I really don't manage to fix is how to get the values from the DialogApp into my function.

classdef DialogApp < matlab.apps.AppBase
    % Properties that correspond to app components
    properties (Access = public)
        UIFigure                        matlab.ui.Figure
        OKButton                        matlab.ui.control.Button
        toolorientationSpinner          matlab.ui.control.Spinner
        toolorientationSpinnerLabel     matlab.ui.control.Label
        speedupdownsampledatabySpinner  matlab.ui.control.Spinner
        speedupdownsampledatabySpinnerLabel  matlab.ui.control.Label
    end
    properties (Access = private)
        CallingApp % Description
    end
    % Callbacks that handle component events
    methods (Access = private)
        % Code that executes after component creation
        function startupFcn(app, mainapp, dby, compass)
            app.CallingApp=mainapp;
        end
        % Button pushed function: OKButton
        function OKButtonPushed(app, event)
            delete(app)
        end
        % Value changed function: speedupdownsampledatabySpinner
        function speedupdownsampledatabySpinnerValueChanged(app, event)
            dby = app.speedupdownsampledatabySpinner.Value;
        end
        % Value changed function: toolorientationSpinner
        function toolorientationSpinnerValueChanged(app, event)
            compass = app.toolorientationSpinner.Value;
        end
    end
    % Component initialization
    methods (Access = private)
        % Create UIFigure and components
        function createComponents(app)
            % Create UIFigure and hide until all components are created
            app.UIFigure = uifigure('Visible', 'off');
            app.UIFigure.Position = [100 100 254 226];
            app.UIFigure.Name = 'MATLAB App';
            % Create speedupdownsampledatabySpinnerLabel
            app.speedupdownsampledatabySpinnerLabel = uilabel(app.UIFigure);
            app.speedupdownsampledatabySpinnerLabel.HorizontalAlignment = 'center';
            app.speedupdownsampledatabySpinnerLabel.Position = [40 173 176 45];
            app.speedupdownsampledatabySpinnerLabel.Text = {'speed up '; '(downsample data by:)'};
            % Create speedupdownsampledatabySpinner
            app.speedupdownsampledatabySpinner = uispinner(app.UIFigure);
            app.speedupdownsampledatabySpinner.Limits = [1 10000];
            app.speedupdownsampledatabySpinner.RoundFractionalValues = 'on';
            app.speedupdownsampledatabySpinner.ValueChangedFcn = createCallbackFcn(app, @speedupdownsampledatabySpinnerValueChanged, true);
            app.speedupdownsampledatabySpinner.HorizontalAlignment = 'center';
            app.speedupdownsampledatabySpinner.Position = [84 155 103 22];
            app.speedupdownsampledatabySpinner.Value = 1;
            % Create toolorientationSpinnerLabel
            app.toolorientationSpinnerLabel = uilabel(app.UIFigure);
            app.toolorientationSpinnerLabel.HorizontalAlignment = 'right';
            app.toolorientationSpinnerLabel.Position = [86 80 84 22];
            app.toolorientationSpinnerLabel.Text = 'tool orientation';
            % Create toolorientationSpinner
            app.toolorientationSpinner = uispinner(app.UIFigure);
            app.toolorientationSpinner.Limits = [0 360];
            app.toolorientationSpinner.ValueChangedFcn = createCallbackFcn(app, @toolorientationSpinnerValueChanged, true);
            app.toolorientationSpinner.Position = [86 105 84 22];
            % Create OKButton
            app.OKButton = uibutton(app.UIFigure, 'push');
            app.OKButton.ButtonPushedFcn = createCallbackFcn(app, @OKButtonPushed, true);
            app.OKButton.FontWeight = 'bold';
            app.OKButton.Position = [52 18 151 39];
            app.OKButton.Text = 'OK';
            % Show the figure after all components are created
            app.UIFigure.Visible = 'on';
        end
    end
    % App creation and deletion
    methods (Access = public)
        % Construct app
        function app = DialogApp(varargin)
            % Create UIFigure and components
            createComponents(app)
            % Register the app with App Designer
            registerApp(app, app.UIFigure)
            % Execute the startup function
            runStartupFcn(app, @(app)startupFcn(app, varargin{:}))
            if nargout == 0
                clear app
            end
        end
        % Code that executes before app deletion
        function delete(app)
            % Delete UIFigure when app is deleted
            delete(app.UIFigure)
        end
    end
end




