Why do catholic believe they can be bad and just believe in god and this sends them to heaven ?

Because that's what the Bible says

WHAT IS THE CONDITION OF THE DEAD? Humans are made from dust. ( Genesis 2;7; 3:19) We are not spirits living in a body of flesh. We are physical creatures, so no part of us survives death. When we die, our brain dies too, and our thoughts perish. Thus, Lazarus said nothing about his experience of death because the dead are unconscious. Read Psalm 146:4; Ecclesiastes 9:5,6,10.... Dose God torment people with fire after death? Since the Bible shows that the dead are unconscious, hellfire is clearly a false teaching that slanders God. The very idea of tormenting people with fire disgust him. Read Jeremiah 7:31... WHO WILL RETURN TO LIFE? Many millions of people who are dead in the grave will return to life on earth. Even some who did not know God and who practiced bad things will be resurrected. Read Luke 23:43; Acts 24:15. .. Resurrected ones will be able to learn the truth about God and to exercise faith in Jesus by obeying him. ( Revelation 20 :11-13) Those who return to life and do good things will be able to enjoy life forever on earth. Read John 5;28,29... For more information JW.ORG

Some of us, not just Catholics, think that whatever they do is right.

So, your aunt is your source of information about what the Catholic Church teaches?? The Catholic Church teaches that we must repent of our sins and receive God's forgiveness, in order to be saved. And that we can turn away from God and forfeit salvation at any point in our life. Jesus is the one source of our salvation, and sin is a rejection of His teaching. Which is why Jesus provided us with a source of His forgiveness, telling the Apostles, the first priests of His Church, "Whose sins you forgive, they are forgiven them". Better find yourself a more reliable source of information.

They don't.  Use the brain God gave you.

That is nothing even close to what we actually believe . You obviously never went to catechism classes did you.

If only Catholics took the time to study the Bible and believe it, they would discover that even the demons believe in one God, but they know they're heading to the lake of fire. James 2:19 and the whole book shows what will happen to religious hypocrites. Nobody can get to heaven by what they do, or what they believe. They only get in by God pardoning all their sins when they repent and trust in what Jesus did to save them. They cannot save themselves. Their Catholic religion cannot save them. Their pope cannot save them. If they just read the Bible they would discover that! But no, they think they go through the motions of being a Catholic and no more is required. What blindness! The Bible would open their eyes.

It is not enough to believe in God to be Saved, you have to obey his commandments. Demons also believe in God, but they will be condemned to hell after this earthly life along with millions of Humans.

"Faith alone" is mostly a Protestant teaching.  "Faith alone" Protestants generally claim that Catholics believe good works will get them to heaven.  You have something backwards there.

This is common across Christianity in general. I knew some West Virginians who were some other Christian and they loved to commit lust (deadly sin) and were racist. They couldn't handle South Park because of how often "god dammit" was said, but they had nothing against sinning in other ways. They simply believed as long as you went to confession god will forgive you. God quit forgiving them years ago.