Welcome to the Julia Discourse! You’ve posted quite a bit of code for people to go through, you might want to consider checking out Please read: make it easier to help you and follow the tips there to amend your question to increase the chance of getting help quickly.
With that said, your code errors because you are trying to convert a complex number into a floating point number somewhere, which doesn’t work. An MWE for this would be:
julia> a = 1.0 + 1im
1.0 + 1.0im
julia> typeof(a)
Complex{Float64}
julia> Float64(a)
ERROR: InexactError: Float64(1.0 + 1.0im)
Stacktrace:
[1] Float64(::Complex{Float64}) at .\complex.jl:37
[2] top-level scope at REPL[3]:100
You would therefore have to think about where this conversion happens and why.
Also, while it is fine to ask for help with your homework here on Discourse, you might want to have a look at our informal homework policy here: Homework policy - #17 by Tamas_Papp