Moving & Setting navigation nodes in different Functions

So Im currently making a Simulation game.

I've started to make my own systems, instead of looking up tutorials (which may or may not was a good idea). So I made my own navigation system which is briefly this:

Get the Node by the name of XY

Set that node as the TARGET

Move Towards the target

And it repeats itself

My move "NPC to the node" code is in Update (which is moves the NPC towars the TARGET), so I can just set the TARGET in function A. The problem is, when I have a multiple chain of nodes, I tried making a system wheres "If NPC's position is equal to Targets, set the next target" But that didnt quite worked out. I tried using While loops in function A, it does everything in an instant.

So, anyone can help how can I make this system possible?