I'd avoid this phone like the plague. It has slower "read/write" than my 12C, which is already paaainfully slow compared to my +6 year old Mi 9T. I can't image how slow the 15C is.
Anyone wanting an ultra-cheap phone, they'll end up with much better performance from a 2nd hand mid-tier phone than with these ultra-cheap phones. Stay away from them!
I only kept the 12C because it's used for a very static usage (secondary/terciary phone), but if I had to use it as a primary phone, I would have returned it right away.
The Redmi 15C 4G offers a lot for very little money: A PWM-free 120 Hz screen, for example, and a large battery. If you want a large screen, you will also get your money's worth, but there are also disadvantages to the inexpensive phone.