Dealing with death in the family

I have never really dealt with death. I mean dealing with the feeling of someone passing away. I never really experienced grief.
The first time I experienced someone close to me passing away was my grandfather. That was almost a decade away. I was too young to understand it and grief. I just knew that he had passed away. We had a funeral. I knew my mum was very very sad. I could feel the grief during the funeral. But I didn’t understand grief myself.
Since my grandfather passed away, I hadn’t dealt with anyone close to me passing away. I have heard about the news of distant relatives passing away. But none that lead me to think about grief. Until today. Today one of my close cousins passed away. He passed away in rather unfortunate events. It was a bus accident. One which could have been avoided if fate was on his side.
I got the news as I was getting ready for work. It was 3 am back in Bangladesh, 6 am here in Japan. I was about to get into the shower when I got this text from Dad.
I didn’t know how to react to it. I was shocked and numb. I didn’t know how to respond to the text so I gave him a call and got to know the details. The details didn’t help either. For the next 24 hours, I contemplated how to react. I went about my day normally but in the back of my head, I did have this shadow. This shadow of grief. I was trying to grieve, but I didn’t know how. I had a call with my mum at night. She knew how to grieve. You could hear it in her voice. But for me, I was still new to it.
I am at a weird stage in my life. I am reaching my 30s in 3 years. This means a lot of my relatives or people my parent’s age will be reaching their 50s and 60s. Back in Bangladesh that is the age when most people’s lives start slowing down and you start to hear about the death in the family. So I do need to get used to grieving. I don’t even know if I am making sense. Let me know how you deal with grief.