I think I got it now :/ it quite confusing.
At low frequence it will have a longer time to charge the capacitor, and therefore the reactans (ohm) will increase, the capacitor will then be able to work as open ciruit and not let the low frequnze through. The low frequence will be lead to the output.
When using a high frequence, there is a shorter time to charge the capacitor before it begins discharging. Therefore it wont charge up the capacitor much and the reactans wont be high (ohm) throguh the capacitor tus leading high frequencies through the capacitor and nothing to the output.
Can anyone confirm this?