Have a play button on some part of the web (and of the app), when you press it, it start the pomodoro and show you a list of the tasks you have to do. When the pomodoro ends you can mark as done the tasks you did or mark them while the pomodoro is running.

This could be an option, i mean let the user choose if have the pomodoro visible or not

this could work with the feature request "rewards". If you compleate a pomodoro it give you some points, if you break the pomodoro then it take you points. That would make it even more satisfactory to finish pomodoros, and because of that, it would make it more easy to focus.

This is good for the people that have it hard to focus to make a task, because you only have to focus for 25 minutes (or you can change this to start more easy) then you can rest for 5 minutos or a little more. And after 3 times of 25 minutes (3 pomodoros) then you have a long break to rest.

So then you do not have the stress of see you have too much to do and can not focus for a long time, like for example studying: If you are not used to study 2 hours a day, then would be hard to do it at the start. So if you focus just a few minutes and have little breaks, would be a lot easier study that time.

https://en.wikipedia.org/wiki/Pomodoro_Technique

Web examples that use pomodoro:
https://tomato-timer.com/
https://pomodoro-tracker.com/