Looking for task/exercise logging app with timer

[MoaPs]

Hi,

I do some exercises every day, for instance:

1 hour fitness training block, split up into
- 10 min Exercise A
- 5 min Exercise B
- 15 min Exercise C
- 10 min Exercise D
- 20 min Exercise E

or guitar playing block:
- 5 min technique
- 10 min practice song A
- 10 min scales

The exercises are not at a fixed time (they can be at 10:00 in the morning or any other time) but they have a fixed duration.
At the moment I use a timer and when the time for the exercise has finished then I change the timer's time for the next exercise until the whole exercise block is finished. Then I log the exercise in a simple Excel spreadsheet.

I am pretty sure that there exist apps (Android, iOS, Web) for this task but I could not find one. In detail I am looking for an app which does this:
- Define task blocks with sub tasks (as shown above).
- Start a task block at an arbitrary time. A timer should automatically set its duration to the sub-task duration.

Has anyone a suggestion for suitable apps/online services?

Regards,