Old Metro Theme Update or reinstalling

I have taken over a website that was created with the theme “Metro” in 2016. Some things do not work anymore. I saw that there is a version for sale (from 2017). What is the best way to proceed?
Buy the license for the theme from 2017, download and install? … or do I then have to set everything again on the existing site?
Thank you for your help!

I would suggest to contact the author who should be able to recommend the best course of action. However, if you don’t have an access to account with which the license was bought with, you will almost certainly have to buy your own license to update the theme.

Thank you, I will buy my own license.