How can I get 650 within 50days?

hi, I'm not English-Native.
I took GMAT prep, I got only 450. My Verbal score only 5. It's very LOW!
AWA 5.0 and IR 4

I don't know how should I prepare for Verbal. I bought GMAT Official Verbal and some Manhattan.
I read the grammar and understand them. The big problem is when I start with question. I alway choose wrong answer.
For example, Sentence correction I found mistake but I feel I get used to A sentence more than B. But A is wrong.
In critical reasoning, I cannot give any correct answer at all.
In reading, I have problem with finding purpose and argument.

I got 7.5 on IELTS test but GMAT is totally different. I have been studying in English School more than 20 years.
I register for GMAT exam on Aug already. If I won't pass this GMAT, I have to give up my Master automatically.

Can you please suggest me some tips or good practice styles?

Thank you so much