Hi Fah,
As you see the dimentions of the window is not correct.
Do you have trim on all sides of the window?
Inside and outside trim must be 120mm deep and the window including trim must be 1800mm X 900mm
The trim must also have replaceable material for inside and outside, ogre – unity and photo.
Attached is a document with all the windows Mr. Tee made.
You will find the window NYS-01 as the first on page 16.
On top of this page you will also see the measurements of these Modern Sliding Windows
Trim:20 mm, Frame: 10mm, Sash:50mm, Left window facing in
Here are also some essential cuts from the windows-manual: