My favourite website that I've found for this is: https://pomofocus.io/Pomodoro Technique
Each ‘pomodoro’ is 25 minutes long so you work for 25 minutes then take a 5 min break
Repeat for about about 4 pomodoros then take a 15-20 break
The idea behind it is you’re effectively working to a 25 minute deadline so become more productive but it is SO important to take the 5 minute break, so easy to just work through but without the technique I always felt sluggish and started to drift/procrastinate working for hours on end
The 5 minute break can be a toilet break/walk or quickly make a tea
You can set a timer on your phone or there is apps you can use!
You can track your to do list as you go and it predicts how long your tasks will take, if that kind of thing works for you!