How to track the project or task time in hours

As has been mentioned what you are looking for is in MS Project (web version can also be added as tab in with Teams). It offers more features than Planner with task dependencies, sub-tasks, gantt chart etc. If you can't afford it, you can use Lists to create your own columns and power automate for the notifications but you won't have the kanban board view.
You can also stick to Planner and add the time/effort in the task Notes field. If you want to capture text as well as effort you can do it by adding a delimiter such as "my text | 1.5" to track a 1.5 hour effort.
The field value can then be split in 2 separate columns for calculations after exporting the plan to Excel. You could actually use as many delimiters as you want columns in Excel.
It's a shame that Sharepoint classic task list that has most of the Project for the web features but for free has not been turned into a modern list/webpart.