Could anybody explain the role of religion in a person's life?

Actually, animals don't live in harmony;). Re. the role of religion, I don't think one person can come up with an answer for another, nor are all religions the same in essence. Now, the background of your question assumes a certain view which seems to presuppose something, that religion is not true. That may be the wrong place to start with the question, in all fairness, because you would be considering the merit of religion as a use, and ignoring what a religion claims that it might be true.

Religion is avery sensitive topic.

Sometimes the conflict is a mask. People will use religion as a excuse when the conflict is really about something else. Greed or to dominate.

I became a Christian many years ago and can honestly say that without the "peace of God that passes all understanding" I would have never retained my sanity through the loss of a precious sister, nephew, two husbands and both parents through the years. Having a personal relationship with the Father God through the sacrifice made by His Son Jesus on the cross, is not 'practicing a religion' but living life fully both now and eternally.

Religion is god..But nowadays it becomes a reason for fight

People need something to believe in. Most of all, they need to believe that there is an entity that's looking out for them. The sense of security this imparts, though not so validated, is vital for maintaining the peace of mind.