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.