Can I combine narrow wide chainring in triple chainring? I have Shimano crank (MT300) with triple chainring (44-32-22), I want to change the outer chainring(44) with the bigger (maybe 50 or 52), can I use narrow wide chainring in outer gear? so the new set up will be (50-32-22). Any problem with shifting up and down after I use that new chainring?
Narrow-wide chainrings are specifically designed for single chainring drivetrains and cannot be used on double or triple derailleur cranks. A 50 tooth ring won't work on your setup either.

Narrow-wide chainrings are designed specifically to stop the chain coming off them, which is exactly what you don't want in a derailleur drivetrain. The derailleur likely will not be able to pull the chain off of or onto the ring at all.

Regular chainrings (and cassette sprockets) have ramps on the inner surface and specially profiled teeth which help the chain hop on and off the ring. A narrow-wide ring lacks those features that and has taller teeth that protrude further through the chain links.

Narrow-wide rings of course have alternating narrow and wide teeth that fit between the alternating inner and outer plates of the chain. If a derailleur were able to shift the chain into a a narrow-wide ring, half the time the teeth and chain links would be mis-aligned and the chain would not be able to drop onto the teeth.  

Front derailleurs have a total capacity limit, which is the difference in number of teeth (and hence diameter) between the smallest and largest rings. if you put a 50 tooth ring on the crank you'll have to move the derailleur up on the frame, and the cage will not reach the smallest ring. Additionally the 32-50 tooth size difference between the middle and outer rings would be too large to get the chain to shift properly. 

And, mountain bikes typically don't have chain-stay clearance for a 50 tooth ring.