ok, after a bit of looking I found that you can set the UOM of the products. You first have to check the Unit of measure checkbox in the sales-settings. Then you can set the different uom's you like at the product. For setting the precision I still haven't found the solution. I can change the precision for all the products, but this is not usefull. For some products I like normal numbers like: 1 bottle of milk. We are not going to sell 0.5 bottles of milk. But for other products I like to set comma numbers. Like 0,5h of work. Anybody has an Idea where you can set that?

settings ->sales -> uom