You can book the working time directly on tasks. The task is linked to a project so that the time is posted to the project.
To start the timer, press the green "Play" button in your task list.
The task and the corresponding timestamp appear in your timestamp list. To display the column "Task", right-click a column header.
To evaluate the task and the recorded times, grouping by "task" in the timestamp list makes sense.
Also in the task properties you have the opportunity to view the recorded times of the task. Switch to the tab "Times". And again, the familiar filter and grouping options are available again.