Finally bought oppo k13

Finally purchased it.. saw few issues already. I am getting eye strain looking at the screen idk why? But on other hand i have the realme 11 pro which i have been using for 2 yrs & never faced anything like that.. another thing during 1 night i see 10 % idle battery drain.. i don't know yet what causes it.. network on 2g, no recent app , dark mode no wifi or bluetooth on still y is that? Anyone faces?