Wonderful work, Uros. I hope you decide to open both sliding windows, work like that shouldn't be hidden.
How about if you cut out the sliding windows, then make a new, thinner window out of some clear styrene, then cut the new window in half and attach the front part to the rear of the opening so the window looks half open?
How about if you cut out the sliding windows, then make a new, thinner window out of some clear styrene, then cut the new window in half and attach the front part to the rear of the opening so the window looks half open?