504 & 505 Errors, Slow Imports Via CSV

I am trying to import content to my site and am having problems. I started my first import 5 days ago. As suggested in the tutorial, I started with importing venues.
(1) the system did import duplicates and I have spent the last couple days removing the duplicates. I thought I saw somewhere and selected it to not import duplicates. Did I incorrectly see this option? I have the basic events calendar that comes with the iVent theme, not pro.
(2) The system is still working on importing. I started this 5 days ago. Is this common to take so long? It is a huge file (60,000 lines of entries) but I didn’t expect it to take this long. Is this normal? If not, what can be done to speed up that process.
(3) Since starting the import, I have been repeatedly getting 504 errors while trying to work on my site. I have also gotten 405 and 505 errors. My hosting company says they’re not seeing any issues on their end as they can view the site on the front end. My issues are occurring on the backend. Can you please look into this and provide suggestions? It has been a beast trying to work on my site since this has been happening. FYI: The actions that I have been trying to do and are resulting in 504 errors and other errors have to do with venues; I was attempting to delete the duplicates (using the Fix Duplicates plugin) or trying to publish the venues using the bulk edit function of venue posts.

I see there is an update available as of yesterday. However, reading the details of the update, it does not appear that the update will fix my issues. As I said, the import is still going. Should I wait for the import to finish before updating? I don’t want to lose the content from the past 5 days of importing.

Please advise on all of the above. Thanks in advance for your prompt response.