If time-tracking it is what you need for control of your work, then this application for you.
With Easy Time Tracker you can track time of multiple tasks and subtasks. 

Features:
• Multiple tasks;
• You can add subtasks for each task and track time of the each subtask;
• You can set the limit of time for each task;
• Limit of time can work as countdown;
• You can pin tasks at top of the list; 
• You can sort tasks and subtasks by drag and drop as you want;
• You can hide subtasks at the task list;
• If you click on tracked time on the task you can see full log of tracked time;
• In the log of time you can add manual correction of time;
• Active task notification is shown at the notification bar;
• Statistic reports by tasks and by intervals;
• Support of multi-window mode for some Samsung devices;
• Sound or voice notification about the active timer;
• Ads free.