Q: I have a macbook pro to buy in 2011 and would replace it with a new one, take it as part payment?

Apple doesn't have a trade in policy.

For financing services info:

http://www.apple.com/financing/

If your 2011 Macbook is operating you could try selling it yourself to a third party, then apply the proceeds from your sale to a new Mac.

But first read this:

What to do before selling or giving away your Mac - Apple Support

Note all the steps within the above link, such as

Learn how to move your files to your new Mac. Do this before you erase the hard drive or follow any other steps.

Here is another article:

https://www.macbookproslow.com/steps-take-before-recycling/

http://www.apple.com/recycling/