do i just hook the arduino nano to the computer and run the code with fritzing to be able to simulate if it’s working correctly? FYI i already have the breadboard (with the components) built on fritzing
Unfortunately no. The code loading portion of Fritzing isn’t finished and doesn’t at present work for the Arduino (some of the others do work). There is also no simulation in Fritzing so you would need to use the Arduino IDE (or one of the others) to compile and load the program in to the nano and then test it on the breadboard outside of Fritzing to see if it works.
are there programs like fritzing but also simulates it working?
There may be (although Fritzing is the only one I know of with a breadboard mode), but if so I don’t know of them. Simulation of programs is generally fairly complex. Perhaps someone else may have some suggestions and we will all learn .
I think people use falstad, but it’s pretty complex for me.
falstad looks (from the initial screen) to be a graphical interface to spice. I such a case it is very unlikely that it will simulate a CPU (the cpu is too complex) which I think is what the OP is looking for. I know there is a simulator for the PIC CPUs from Microchip, but I don’t know of one for the Amtel CPUs (although there may well be one somewhere).