You should put your computer on focus assist (windows 10) or ‘do not disturb’ (apple) mode so it blocks all notifications. Also, you should hide your bookmarks bar so YouTube and Facebook tabs can’t tempt you.
I put my headphones on and close all programs I’m not using. When people see me with headphones on they are less likely to bother me.
I put my phone in 'Do not Disturb' mode and let it facing down. In the computer, I use Windows 10 and it has a 'Focus Assistant', which blocks notifications while activated. In Chrome, I never use notifications anyway. If there are people around, I use my earphones and tune to Lo-fi Hip-hop or Classical music, which I find very helpful for focusing. Then I open Word, Excel, PDFs, webpages, everything I know I'll need and only then I start counting time.
Get a pair of Noise cancelling headphones and listen to classical/binaural music. The fabulous app has a selection of binaural music, if I’m not mistaken.
Set a goal for that deep work sesssion to help keep you focused while using a computer. Ex: I will finish 2 reports in the next 45 minutes. Also, consider working on a computer in a public place where others can see what you are doing—this may discourage you from watching YouTube or reading Buzzfeed when you’re supposed to be working. Finally, play simple study music or white noise to drown out sounds around you stay focused. If you habitually use the same music during periods of focus, this may help your body associate that sound with deep concentration and make it easier to get started.
I will put 25 minutes on a timer, usually my phone, and I will not open or respond to anything or anyone until after the timer goes off. I also make sure my phone is on vibrate
I have an aresenal of apps that prevent digital distractions. I use app blockers including Cold Turkey and Rescuetime to prevent me from going to distracting sites instead of working. I also have found online study groups where the members keep each other accountable and sometimes also use shared pomodoro timers. You may even be able to find a real life study buddy or "body double" who can nudge you in the right direction when you get distracted
Perhaps some earplugs or headphones might help. Also, make a commitment to check your breathing regularly. Deal with distractions by taking breaks where distractions are allowed and then promptly get back to work. A timer might help to.
I'd suggest isolating over-ear headphones and instrumental only music