I will try to explain baptism but don't have enough time right now to do a lot of scripture quoting.
Anyway. Baptism is fundamentally not our work. We see that we are told to be baptized, a passive statement rather than to baptize ourselves which would be active and make baptism our work. Baptism is not our work. Rather is is something done to us that we receive through faith.
Since the promise of forgiveness of sins is attached by scripture to baptism. We see how it fits in, that baptism is not really done by us but is done to us by God. God washes us, he sprinkles us clean, he unites us in the death and resurrection of Christ.
Of course we do not receive this saving grace if we have no faith, for grace comes to us through faith.
Some object that infants cannot have faith, but scripture clearly indicates that they do.
Some object that infants are sinless and not in need of saving, but scripture teaches that all have sinned and indeed the original sin is transmitted to us all.
The normal pattern we see in the Bible is baptism of a whole families or households or even nations.
Many object to baptism as a means of grace on the groups on their belief in once saved always saved. Lutherans do not believe in that doctrine or it's many forms.
Mode of baptism is not important, sprinkling and pouring are both clear, submersion is not as attested to in scripture, but is within the meaning of the word and so is also accepted.
People write entire books on this, is there a particular thing that you are questioning?
Marv