Mi 4 is a product of Xiaomi which is these days one of the most popular brand in mobile phones with many variants and sizes.
Mi4 is one of the low budget phones from Xiaomi which comes for 7500 INR with pretty good features but as the price of the phone is less the performance of the phone also gets effected as it doesnt gives quick responses and is slower than many other phones and if you are switching from some other phone of 10k except samsung which lags alot then you will definately find mi4 slower than that.
Apart from speed its screen is small which is handy but at the same time the internet surfing and playing games are not that fun with mi4.
If you are low on budget then you can give it a try.
Thank you