Is it healthy to lose 6kilos in a month for a 55kg and 150cm girl Will it not effect my body if I suddenly lose weight Like stretch marks and so Is it okay I want to lose weight so please?

First off, i doubt if you really need to lose any at all. Check where you're at in a BMI chart before proceeding.

But if you insist, that's a bit more than 10% of your body weight, and that should disappear fairly unnoticed.

But losing 1.5 kg/week for someone who is 55 kg is HUGE. You'd have to use a CRAZY strict diet to pull that off. At the very least, give yourself more time. Even 0.5 kg/week would be OK.