Excel is not native on a Mac, so it's bounded to be slow - especially if you're using it on an old machine. As I see it, you have two options: 1) Upgrade to Office.
When I had a similar problem, disabling dropbox integration (I never realized I had enabled it) made a huge difference in performance, especially for otherwise trivial things in Office/Excel like copy and paste (which had become unbearable). System Preferences->Security & Privacy->Privacy Tab->'Allow the apps below to control your computer' (dropbox was checked, I unchecked it).
Not sure exactly what functionality this took away from dropbox, but it still syncs folders fine, which is all I used it for anyway. (I know this is thread is over a year old, but it's one of the first results in Google so I'm adding this for all the others who come along in hopes it may help them).
I believe there is an out of control process causing this that needs to be force quit to get performance back to normal. Here are my online findings on the topic: • • • The comments hint towards too many 'open ports'. Microsoft access. Force quitting the excel process via activity monitor with the most ports seems to do the job. I suspect this is a registration connection issue. Office tries to constantly connect home and check that the product is registered. If you are offline and then go online then the issue occurs.
I'm guessing these open ports are in reference to internet connections to a registration server. I have Office 365 Excel 16.10 running on High Sierra (10.13.3). Copying takes several seconds, sometimes cell comments are not viewable at all & often my previously working Hyperlinks to other files in the same folder don't work.
Neither unfreezing pans/rows, adding Excel to System Preferences > Security & Privacy > Privacy Tab > Accessibility nor using Normal View (my standard anyway) made any improvement in its performance. I didn't have Dropbox in my Privacy list. Disconnecting from the internet improved the situation, however. Copying is a little quicker, although viewing comments and using Hyperlinks are still unreliable. I have to say that I don't consider this a practical solution, merely a workaround while waiting for Microsoft to fix the problem.
It seems that one of the surprises with Safari 10 on Mac OS Sierra is that it takes ages to perform a search using the search bar (using Google as default search engine). It takes on average even more than 5 seconds to open the new search tab with google results. I would rule out a system issue because I reinstalled the entire OS from scratch less than a week ago.
This issue didn't change at all. The only extensions that I am using are 1Password, LastPas and 1Blocker. I tried using the search on private mode and it seems to get the same slow results so it should not be related to extensions. Can I make it 1 second? On Chrome it works well.
Just to add a little more context to the other answers, below are the official descriptions of the related settings. I don't care two cents for either of these 'features', so I disabled them both, and I saw a significant improvement in search speeds. Enable Quick Website Search Lets Safari record information about your searches within a website to expedite later searches on that site. You can then search within that website by entering the name of the site, followed by your search term, in the Smart Search field.
Click Manage Websites to see or remove websites for which Safari recorded Quick Website Search information. Preload Top Hit in the background Lets Safari start to load a webpage as soon as it determines a top search hit based on your bookmarks and browsing history.