You can use the 'Task' column of your table as x-data for 'barh' function. You can make it a categorical array using the 'categorical' function. But to make it a categorical array, the array should have unique values.
I followed this approach for the csv file provided by you
rd = readtable('Gant.csv'); %read data from the csv file
xVals = categorical(unique(rd.Task,'stable')); % 'stable' preserves the order
After this, you can create a m x n matrix using 'Start' and 'Duration_months_' columns to plot the values. Since, the 3rd task above has two entries, we need to create a 9x4 matrix. 9 rows for 9 tasks. Out of 4 columns, first two columns for first entry of task (Start,Duration), next two for the next entry. Since only one task has a second entry, other tasks can have zeros.
A = double(rd.Start);
B = double(rd.Duration_months_);
C = zeros(9,1); %initialize with zeros
D = zeros(9,1);
% assign second entry to C and D arrays, i.e. the 5th entry to 3rd position
C(3,1) = A(5,1);
A = [A(1:4) ; A(6:10)]; % reshape A to have 9 values
D(3,1) = B(5,1);
B = [B(1,4) ; B(6:10)]; % reshape B to have 9 values
% plot
barh(xVals, [A B C D], 'stacked');
Hope this helps.