If penis in vagina occurred yesterday (20th april) with ejaculation, and 4 days later (24th april), girlfriends period came would that mean that sperm that was ejaculated in her would die on girlfriends 2nd day of period (25th april)?

The life span of sperm ejaculated in semen is 24-48 hours at body temperature. The sperm should have died by the time she had her period.

Rarely, sperms can survive up to 5 days in the female genital tract after the ejaculation so yes, by day 25th most of not are all already dead. However, I still wonder how you can predict her period in 4 days or this question is for an event in April 2022. Take care.