Can someone help me answer this question? It's combining like terms, my teacher said that the first term is right but the rest is wrong.

Question~~
2x^2y–5xy–7xy–8x^2y+9xy^2 –xy^2

My answer ~~
2x^2+-8x^2
(2-8)x^2
-6x^2
y+y+y+y
(1+1+1+1)y
4y
-5x+-7x+9x+-x
(-5-7+9-1)x
-4x
y^2+7^2
(1+1)y^2
2y^2
The answer that I got is~~ -6x^2+2y^2+4y-4x