Associate a task with both a work resource and a cost, and sign 100% completed activity

Marco_Vendra,
For future questions please use English.

Cost resources are not tied to task effort (work) or duration, so they will be independent of percent work complete or percent complete. In order to accrue the actual cost for a cost type resource, you need to enter the value into the Actual Cost field.

Since your scenario is for a rented machine (forklift), you might consider setting it as a work resource with a zero standard rate but with a cost per use value. For example, let's say the forklift rents for $100/day. Each time the forklift is assigned to a task, whether the task is 1 hour or 1 day, the forklift will cost $100. However, note that if the task is a two day task, it will still only accrue a cost of $100, so this method may or may not be appropriate for your needs.

Hope this helps.
John