What would you recommend me in this case ?

Being able to focus so much is generally a valuable strong suit, which few people have. However:

How important are those big problems? If they are important enough, then what there is to do, is simply let everyone know that you have something you need to focus on, and that you are going to do that, and how to reach you IF they have something more important to interrupt you about.

If you are not sure you are right about these problems being worth the focus, then you should think and feel through that. Make it a big problem for yourself, focus, and/or talk to other people who are wise and/or offer balanced or at least contrasting views to help you choose what your priorities are.

Also figure out what other things you want to have enough priority that they don’t get crushed by your focus. Try to sort that out in a way that makes sense and feels right. And then communicate that to the people in your life. e.g. “I sometimes need to focus on important projects, but I’ll let you know that’s what I’m doing, and I may need you to remind me to stop, eat, come to bed, talk to you when you need company, etc. I will also set myself an alarm to interrupt myself and not miss appointments, dates, etc.”

If you determine that you are focusing on some things that don’t deserve that much focus, develop habits that will interrupt you and get you to periodically re-evaluate what you’re choosing to do. And/or get co-workers or partners or friends to help check in with you, give them permission and means to interrupt you, etc.

Find a BALANCE between your “focus” & your other tasks!!! Focus on the “important” task say 7 hours a day & then at the end of the day, check your email, voice mails, & any other part of your job that might need attention. IF you put too much focus on your NEW task & let the rest of your job fall by the wayside, you boss might notice your failure to handle “your job” in total. Your boss will be MORE impressed with your ability to “multitask” than to do just 1 job at a time!!! IF, by chance, the rest of your job falls apart while you’re focusing on one new task, that won’t look good on you!!! I can’t tell you exactly how to handle that part as it’s what works BEST for YOU!!!

I recommend something similar to @LadyMarissa , but with shorter durations.

No matter the size of the task, you work best if you take a short break every hour. So once an hour, take five minutes to scroll through your emails and messages to see if there is something urgent, and also take five minutes to stand and get some water,

That way, people won’t think you are ignoring them, plus you will do better on the big project.

Also, communicate with your boss on what you are spending your time on and why it takes so long.

I agree with @zenvelo. Set aside project time each day when you are more available, so you don’t miss other smaller tasks.

I have a project due 4.25 so I work on that on my 2 slowest days of the week for about 3 hours a day. In my position ignoring other work results in lost revenue which is unacceptable.

Most tasks in life contain moments where you have to wait for something to happen.
During those natural breaks, you can then complete your smaller tasks.
I think you are doing what you do…. to maintain focus. Overall this is good.
Most people prefer to multitask, but most people are scatterbrained as well.
I am assuming you are less scatterbrained than others. But you can still complete smaller tasks, or get the tasks at least started, during breaks in the Big Task.

I go one step further, if I have a hard task to finish, it even effects my private life; I stop going out or doing things until I am done with that hard task.

The brain sometimes NEEDS a break!!! You can focus while working but should break that focus for 5–15 minutes without totally losing the idea of your end goal. Taking a 12–16 hour break overnight can work to recharge the brain for better ideas the next day!!! Staying so totally focused 24/7 isn’t good for your health either as it can increase your stress level.