Bending bars of iron gate
You can use what's called a "come along", it's a portable hand operated winch-like tool for moving things short distances with a lot of force. The thing is, you will need to find a point at which to anchor one end that is significantly stronger than the bar, like a fence post, otherwise if you just connect to another bar just like it, you bend them both.



This video shows the general operation of it, you would need to adapt to your situation. Small light duty ones are inexpensive or in many cases you can rent one from a rental yard.

https://www.youtube.com/watch?v=6FfVsfto7-g