In my articles I would like to show a price table which is subject to currency exchange. By changing 1 number in the back-end the price in all articles has to be recalculated in one time. For example 1000/40 = 25 Euro.

Will this be possible by K2? With an extra field for example?

You need to look for an extension at the JED or at getk2.org/extend

Thanks, i did visit this extension site already. I find many extensions about search and filter in which visitors can make a selection.

But that is not what I am looking for. I just want to show my prices in a table with the possibility to change the rate in a variable field.

Hereby I would like to find out if this is possible by K2. For example with the extra field. Or maybe other forum members have experience with a plugin which makes this possible. For example a filter that find our prices without any selection from the visitor.

I attached an example which I create in Google Sheet. By K2 I hope to find a better, more professional way.

Outputting directly extrafields is very easy and you can find several topics in this forum.
You can aslo override the extrafields foreach loop in item.php and turn it in a table.

But you have to get the rates somehow from an external feed.

So you have to parse that feed (can be ,xml, .json whatever ) and then write a small JS snippet to recalculate the rates.