adsense; 3 columns to 2 columns; date removal

Hello,
I have four questions.
1. This theme: https://wp-themes.com/bible-scholar/
Has three columns. I want to make it 2 columns. One side bar on right side.
– how to do that

2. this theme doesn’t have adsense. https://wp-themes.com/simplish/
How to make it adsense ready.

3. If I want to post without date, what code changes do I need to make

4. what is the best source for learning how to customize the wordpress theme.

thanks.