You're better off with a fresh install, to be honest. Otherwise, you will have to upgrade to the next version, one at a time.

And how do you keep all the information?

If you want to keep all your information, just update (one version at a time, it's just 2 versions anyway) to 5.3.2, once you're done, you can skip all the way to the latest stable version: 5.4.2.2

If you need help, contact me, I'm currently writing a tutorial on this. Also, I could update it for you.

5.4.2.1 Is the latest automatic pushed version if you are worried about things breaking I would recommend waiting until those bugs have been ironed out and then a update option will appear.

/****************************************************/
VERY IMPORTANT: Make sure you back up your database.
/****************************************************/
Use the dashboard to backup the site, and store that somewhere.

To manually upgrade upload a concrete version into your updates folder
in your site.php add the version you are upgrading to
define('DIRNAME_APP_UPDATED', 'concrete5.X.X');
(You can try without running the following line sometime this will work, but the version you are I believe requires some db changes so will probably need the following bit)

I would be very wary about upgrading to the latest 5.5 version though? directly from 5.2, its safer not to.

Add the following to your url /index.php/tools/upgrade?force=1

To roll back you can delete comment out the version in your site.php,
Depending on what changes where made to your database you may need roll back you database.

I would probably do as Nicole suggests and upgrade one version at a time.

But make sure you backup your database!