You should not need to specify a format when reading in the data set, thought I believe you can.
If I am understanding you correctly ``df <- read_excel("Q.xlsx")` is working.
If so, you can change data types in df.
Use
str(df)
or
glimpse(df)
to see what R thinks are your data types. They do basically the same thing but the formatting is slightly different.
It would be very helpful if you supplied us with some sample data.
A handy way to supply some sample data is the dput() function. In the case of a large dataset something like dput(head(mydata, 100)) should supply the data we need. Just do dput(mydata) where mydata is your data. Copy the output and paste it here.
In general, you may find this useful: FAQ: How to do a minimal reproducible example ( reprex ) for beginners