Hello,

JEE Main 2019 exam will be conducted twice in January and April and Yes, you can apply for both the exams. According to the JEE Main Eligibility criteria, you should have secured atleast 75% marks in class 12th examination or be in the top 20 percentile in Class 12th examination (65% in class 12th for SC/ST candidates). Assuming you belong to General or OBC category then your percentage is less  so I would suggest you to apply for the improvement exam to fulfill the eligibility criteria of scoring 75% marks in class 12th. You can apply for improvement exam in one or more subjects in which you have scored less marks.
Good Luck!

Yes, you are eligible to apply. You can check the further eligibility with the given below link.

https://engineering.careers360.com/articles/jee-main-eligibility-criteria

Good Luck!