IELTS - Score - Stuck in Writing & Speaking

[smhamza]

Hello friends

Kindly check out my history of scores:

R 7.5; L 8.5; S 7; W 7 (EXPIRED)
R 8.5; L 8.5; S 7.5; W 6 (2019)
R 8; L 8.5; S 6.5; W 6 (May 23, 2019)

I am struggling to improve my writing score.

Can someone just recommend me what approach to follow, or what book to follow to improve my grip of Writing?

Thanks.