Click in the Project Center in the file menu „Settings“ -> „Additional Settings“.
Select the tab „Estimation“.
Here you find a function called „Don’t save fixed prices after Quotation, Order Confirmation and Invoice“.
In case this checkbox is activated, the changes of the price updates will be kept automatically.
If the function is deactivated, the estimation price is set as fixed price. By using this, the original estimation price will be kept after a price update.
If you set the fixed prices after generating a printout (e.g. quotation, order confirmation or invoice) you have to change this manually for every single position. Otherwise the fixed prices will not be considered.