hello again...
based on my previous suggestion, this will do the trick :
[filename, pathname] = uigetfile('*.xlsx', 'Bitte Datei aussuchen'); % Leitungen_Auslastung.xlsx
[numericData, ~, rawData] = xlsread(fullfile(pathname, filename));
headers = rawData(1,:); % variable names
comments = rawData(2,:); % comments names / units
Y_legends= headers(2:end);
% replace underscore with blanks for legend strings
Y_legends2 = strrep(Y_legends,'_',' ');
[samples,nrows] = size(numericData);
y = numericData; % rows B and beyong (select rows with N if needed)
date_data = rawData(2:end,1);
dn=datetime(date_data,'InputFormat','yyyy.MM.dd HH.mm.ss');
figure(1),plot(dn,y);
xlabel('Time (s)')
ylabel(' Data');
legend(Y_legends2);
