Without knowing exactly what you need to do, this advice will be pretty general but here goes.
Try and estimate roughly how long each one will take and allocate time accordingly
Try to set aside a specific amount of time during the day that you are going to work on the problem. Personally, I always used to try and think of it like a job, and aimed for around 35 hours a week studying where possible, but I didn't have a job at the time, so adjust accordingly.
I didn't like to do work one thing at a time of I could help it bc it just got boring. So I used to split my time evenly each day between whatever needed doing each day
Work from most boring/least engaging task to most engaging each day. It'll give you something to look forward to when you're slogging through the boring stuff
Don't try and concentrate for more than 90 minutes at a time. It just doesn't work, and a 15 - 20 minute brake every 90 minutes will improve performance
Try to have a designated place where you study with limited distractions. I days used to go into the university library to work
Getting enough to eat and drink and getting enough sleep will improve performance
If you need to listen to music while you work, chose a play list where you don't need to think about what's playing at all
Keep your phone away from you. Ideally, somewhere you'd have to stand up to get to it
If you need anything more specific, I'd need to know exactly what kind of work you're doing