Getting same value of cost fn

hello, please check my code when i am check mse /mae then its not very high for training, test,dev sets but when i am running model for n_iterations and trying to get cost then its giving the same value …is it because of overfitting ???
URL: https://www.kaggle.com/code/satyajeetrai/notebookf516112afd

I see your notebook is on Kaggle.
You’re expected to use Coursera Labs.

Using any other platform runs a risk of mangling your notebook’s metadata, in ways that will make the grader fail.