I heard not sure how correct that after 30 girl will have problem having first kid. is it true?

Not reliably: What is true is 4-5% of all pregnancies at any age have unexpected outcomes.Premature birth, cleft palate, newborn sickness, etc. After 35 you add about 1% to that risk for the effect of advancing age on the risk of a chromosome defect. All pregnancies have some risk, but proper prenatal care can reduce these to a significant degree.