Hi

Minimum age required to be eligible for SBI PO is 21 years and you are only 20, so you are not at all dear to begin your preparation , there are many people who qualify SBI PO etc bank exams in their 1st attempt and that also in just 1 year preparation or even less, so even if you are starting from scratch you have plenty of time to prepare

For your English you can go through following books and master the language

High School English Grammar and Composition by Wren & Martin.
General English by SP Bakshi (Arihant Publication)
Word Power Made Easy by Norman Lewis.

Follow the below tips to prepare :-

First of all go through SBI PO syllabus and its exam pattern

Go through the previous years’ question papers and see the level of difficulty of the question paper so that you can prepare accordingly

You can take help of video tutorials available free on platforms like YouTube as well

Go through newspaper daily for General Knowledge and current affairs

Once you are done with syllabus go through mock test and identify weak areas and work on them




Thank you