You need to tell us what the Excel workbook looks like and show us what you have tried.
Are you dealing with one sheet or many? It it in a standard rectangular layout? What language?
Have a look at FAQ: How to do a minimal reproducible example ( reprex ) for beginners
Much of it will not be relevant to your problem but it should help a bit in formulating the problem.
This recent discussion may help. I think it is mainly about .csv files but much of the discussion should help
How to Read Huge Files With R
OOPS: Forgot a key question: Can you load it in Excel?