ERROR WHILE IMPORTING EXCEL IN SQL

I tried to import excel data into sql. After multiple attempts the data was imported but some total columns are showing only null values. Those total columns do not have any formulas in it. I am facing this issue while importing CSV also. After importing data from CSV all the columns are showing data type varchar(50), and when I'm trying to cast the column in DATE or INT or FLOAT format the below error is showing

Msg 241, Level 16, State 1, Line 5
Conversion failed when converting date and/or time from character string.

Can any one help me in this