I'm looking for a command to use in the terminal or an application that allows me to see everything what is going on on my pc on real time like $ xev but not just for gui facts but for application status, or background processes.
Both Matt and giodamelio made good suggestions. Another good one that allows you to use it as a heads up display(and the one that I use) is
conky. It can display CPU, Temp., Mem, Network Status, Weather, and lots more.
LifeHacker.com has an article about it here:
Here are a few examples of how it can look.
You should be able to get it in the software manager. The configuration it comes with is really basic, but as you'll see, there's a lot of ways to customise it.