‘... when i try 'plot(x,y)' it says I have too many input arguments ..’
You probably have a variable (or your own function) that you named ‘plot’. This is called overshadowing a MATLAB function, and is best absolutely avoided.
To find out what the problem is, type this in your Command Window or a script, then run it:
All of them should share something similar to this path: 'C:\Program Files\MATLAB\R2018b\toolbox\matlab\ ...'
If the first result is:
You have found the problem. You then have to go through your code to find out where it is, and change the name.