In addition to what has been said above, I think it is really relevant that you can charge per hourly rate if you properly estimate how long you're going to take a project. I meant no offense but 2 months for C4D usage is quite low for an experience, unless maybe you have already been with 3D for quite a while now.
I'm speaking for experience. Way back when, I initially charged per hourly rate and pitched a duration. It turned out my offer was too optimistic for my skill set. I ended up doing twice or so for my offered hours. (Although to mitigate I still charged for example 4 hours instead of doing it for 8 hours Hahaha).
My point is if this is your first time or you feel unsure, try having a modest fixed rate. Plus, it gives a better estimate to the client.
Also, don't forget to negotiate for REVISIONS! You certainly don't want to have unlimited revisions.