I have recently quit smoking after 30 years. am i now safe from lung cancer and heart attack?

No but it's good: You've cut your heart attack risk significantly but by no means altogether. The increased cancer risk from smoking lasts for maybe two decades, but again you've reduced it. More important, the fact you stopped smoking guarantees breathing will be easier when you're older and you're more likely to be able to do the things you enjoy. Again, glad you quit.

No: But it is a good start.

Congratulations!: No one is safe, but you will steadily move from very unsafe (all smokers) to safer with each passing year. There is benefit in lung cancer reduction by quitting even up to 65 years of age. Best never to start. I stupidly smoked and quit @ age 33. Latest data say quit before 35, normal risk of non-smoker.