Try the 15:5 minute work habit if doable in your work circumstances. Work for 15 minutes with intense focus then take a 5-minute break.
If 15:5 minute work habit is not doable in your work circumstances then a short break every 30 minutes also creates good results.
Usually, the most you can effectively work with intense focus is 90 minutes. I have found that the shorter the intense focus period the better the outcome.