To delete text to the left of the cursor - Use the Backspace key on your keyboard.
3
Press Backspace key on the keyboard 5 times.
This will delete John and a space after word John
 
To delete a large selection of text, select the text and press the Delete key.
4
Select the first line by clicking the mouse on the left margin of the sentence
I have recently changed my address; please update your database to redirect my mail to my

After selecting the sentence, press Delete key on the keyboard.
 
The text disappears. The remaining text in the line or paragraphs moves to fill the empty space.