Q:

Could you help to identify this WW1 fighter? 

Please help me identify this world war 1 fighter. 

A:

Pretty sure it's an Albatros C.I. Look at the access hatch with the double gills directly behind it, the three metal covers on the engine, the horizontal and vertical black marks on them, the upper wing support ending right between the two metal covers, the front support for the undercarriage ending right before the second gill. 

Albatros C.I (Picture copied from the link above)
The Albatros C.III has a different tail, but that's invisible in the picture above. 
Here is another picture, showing the plane from the other side.  Note the flush radiator on the side of the fuselage. ( image source)

A:

First of all, this is not a fighter, but a C-type airplane.  A C-type was a two-seater and was mostly used for reconnaissance or ground attack.  That it is a German plane is obvious, but the picture leaves out the details like propeller, wings and fin shape which would help in identifying it. 
Noticeable is the six cylinder in-line engine, the triangular fin and the boxy fuselage.  Of particular interest is the position of the horizontal tail which starts well ahead of the vertical.  This restricts the selection to these types:

Albatros C.III
AEG C.IV (but the tail details don't match well)
DFW C.V
Rumpler C.I
Rumpler C.IV to C.VII (they all looked very much alike)

From the limited information available, my best guess is the Rumpler C.I. See below for a side view from this source:

EDIT:
Now that MSalters has posted his answer, I think that he is right.  It looks indeed like an Albatros C.I. I did not include this one in my search.  Silly me.