I am gonna provide you a couple examples that you can use to reproduce the Dorian sound, over the Gm7 chord.
Compare these two scales:

............... G minor Scale= [G-A-Bb-C-D-Eb-F]
............... G dorian mode=[G-A-Bb-C-D-E-F]

The major 6th (E) is what gives you the characteristic Dorian sound,
Play the Gm7 chord, followed by two arpeggios; and finish it with a minor pentatonic scale.

....Gm7............Bbmaj7(#11).............Fmaj9...................A minor Pentatonic scale...........
e---3-----------------------------------------------------------------
B---3-----------------------------------------8-----------------------
G---3-----------------9-------------------9---------------------------
D---3--------------7--------------7--10------------------------5------
A---5--------5--8--------------8-------------------------5--7---------
E---3-----6----------------------------------------5--8---------------


These are three separate examples, so don`t try to play the whole thing thru, play each example separately and hear them against the Gm7 chord.




Hope that helps.


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