Hello Tanya,

It can take 2–3 hours on Colab TPU.

Check our NLP Tutorial: Question Answering System Using BERT + SQuAD On Colab TPU — https://www.pragnakalp.com/nlp-tutorial-setup-question-answering-system-bert-squad-colab-tpu/ which will be helpful to learn how to fine-tune the BERT model on SQuAD dataset using Colab TPU.

Also, our case-study on QnA system could be further helpful to you: https://www.pragnakalp.com/case-study/question-answering-system-in-python-using-bert-nlp/