Whats is the exact cause of uterus cancer?

Many causes: We do not know "exact" cause of uterine cancers. It has to do with genetic makeup, levels of hormones, and age. All these are just predisposing factors, not causes. Any cancer is ultimately caused by genetic mutations in the cells which make them cancerous.

Increase in hormones: As a woman ages, her risk of uterine cancer increases. The lining of the uterine wall is stimulated to grow by female hormones. Being overweigh does increase one's risk of uterine cancer indirectly by increasing female hormone levels, particularly after menopause.