SD Biosensor interview questions

Interview process was good. HR was nice and interviewers were good. I gave interview for about 45 minutes and answered everything that I was asked. They have given me the offer but I am in confusion if I shall join or not.

first the manager will call you and meet interview and then you go to there to get a job what you apply when is your time to work can you work right now? extra work maybe you should, but its ok?