Trying to avoid brute force with if statements

I am trying to avoid a 50ish if statement if possible.

I have attached a sheet with a rough idea what I am trying to attempt. Basically what I am attempting is:
Sheet1 - the data is just entered based on criteria from another sheet
Sheet2 - Row20 data is copied from Sheet3!C3, Sheet3!D3 etc.
Row21 is where the issues arises -

Formula:

=if(Sheet2!B20=Sheet1!B5,Sheet1!B4,if(Sheet2!B20=Sheet1!C5,Sheet1!C4,if(Sheet2!B20=Sheet!1D5,Sheet1!D4 etc.)

- This formula would then be copied across the page in the yellow cells.
It becomes brute force because the sheet this will go into goes up to BJ4/BJ5.

Try this in column B then you can copy and paste it to all the other yellow cells.

Formula:

=INDEX(Sheet1!$B$4:$BJ$4,1,MATCH(B20,Sheet1!$B$5:$BJ$5,0))

The cells in Sheet2 row 20 must be formatted as General. Currently they are Text. As Text, they will not match the values on Sheet1.

Perfect, thank you, one of these days I will eventually learn how to use the Index and match.