How to attain forgiveness of sins

What I understand from this Brother Eli's video:
https://3speak.co/watch?v=fatimajunio/oeqqzwbw

1John 5:16 points out that there's a sin that is mortal and another that is not. There are unintended sins which are due to the weakness of human body. The sins that are not premeditated have a chance of being forgiven.

In a reply to Peter's question in Matthew 18:21-22, Jesus said we should forgive someone up to 70 X 7 times. These are not sins against the Holy Spirit, or unpardonable sins. If the sin is not a greivious one, you can forgive up to 490 times.

This lesson is not encouraging us to sin but, it is suggesting that someone can sin repeatedly in his life.

But, if we commit those unpardonable sins wilfully, Hebrews 10:26-27 states there's no more sacrifice for such sins.