Can a 4th c-section be safe if the last operation was performed 5 years ago?

Safe: Yes, it can be safe. You do not have many choices. Natural vaginal delivery it more risky. No other choices. Be well and good luck.

Maybe; hard to tell: You may not find reliable scientific information to answer your question or make an "informed decision". Since there are probably very few women who have had 3 Cesarian deliveries and who plan another pregnancy, You and your high risk obstetrical team would need to have an open discussion and arrive at a "shared decision".