The Fairphone 6 has 4905 mAh, your Realme has 6500 mAh. Despite the smaller battery, the Fairphone 6 easily lasts a whole day in everyday use, often 1.5 days, and around 6-8 hours with intensive use. The difference to the Realme is noticeable, but not dramatic, as energy management and efficient hardware make up for a lot.