Here are the basics of what the Bible is teaching us (Bible verses are representative and not exhaustive):

We are all born sinners. (Romans 3:23)

We do not deserve God’s forgiveness. We cannot earn it through being a good person because we could never be good enough (Ephesians 2:4-8).

Since we can never be reconciled with God by our own power, and since sin is deserving of death (Romans 6:21, 23), God sent His Son Jesus to be our Redeemer, to pay the penalty of death by His crucifixion and resurrection (Romans 10:9, 1 Peter 1:3), so that we can be reconciled to God (Romans 6:23 and Romans 8:1-2, Ephesians 2:8). Also see Hebrews 11:6.

The good deeds we do as Christians are in service to God and for His glory (Matthew 5:16; Ephesians 2:10). See Galatians 5:17-26 for a contrast between evil deeds (deeds of the flesh) and good deeds (fruit of the Spirit).

You can choose to accept this truth or you can choose to not accept it. By not choosing at all and calling yourself an “agnostic”, you are choosing not to accept it (Revelation 3:16). But it is actually up to God whether or not you do accept the truth of God (Ephesians 1:4).

You are responsible for your choice, in accepting the truth of God or not (Romans 14:12; Galatians 6:7-8).

Choosing not to accept it means eternal death (Romans 2:17-20; 2 Thessalonians 1:8-9). Eternal death is bad (see Revelation 20:14-15). See Luke 16:22-31 for the story of The Rich Man and Lazarus, told by Jesus, in which the rich man ends up in hell.

Hell is eternal and complete separation from God (2 Thessalonians 1:8-9), as well as agony and torture (Matthew 22:13, Luke 16:23-24; Revelation 20:10, 14, 15).