First you have complete your syllabus atleast twice once the concepts are on your tips then uh can last year questions papers which are very important atleast last 3 years paper the more you practice the more chance will be there to clear it .

Hey.

You can use the link below to see the important topics for JEE Mains 2019.

https://www.google.co.in/amp/s/engineering.careers360.com/articles/jee-main-2019%3famp

You can use the link below to see the sample papers for JEE mains.

https://www.google.co.in/amp/s/engineering.careers360.com/articles/jee-main-sample-papers%3famp

Best of luck!