How to stay focus on work?

Setting focus hours would help, combined with 40 min work, 20 min break or whichever intervals suit your concentration span the best.
Setting your devices on silent or do not disturb, and focusing on the thing in front of you would help. Noting that too much focus will ruin you mind as you need a mental break, specially if you are stuck with an issue.
Finally, dedicating a certain space/desk for productivity only, this will train your mind to get into work mode while you are there.

Set it to silent and just check at the time we take a break, and for family of couse we need to communicate it well. Interval that suit for me is using pomodoro technique, get 5 minute little break after 25 minutes of work, and get 20 min break after 3 times little break, actually sometime I skip that little break and adjust it.

One good thing is time schedule. But personally, I was struggling with it, because of my lack of discipline. But then I have heard about good lifehack - plan not your work time, but your rest time. It legalizes your rest hours and makes your rest more efficient: Instead of blaming yourself for rest, you completely switch to it. So it's more easy then to return back to work.
So, start with scheduling one hour of rest in suitable time after some time of work. And then you can add more scheduling (step by step), playing with time periods length, etc.

tea