@Tepichin Here are a few articles that explain blasphemy against the Holy Spirit.
First - I would like to echo a point made by the late R. C. Sproul - “worrying about it is one of the clearest evidences that they have not committed this sin, for those who commit it are so hardened in their hearts they do not care that they commit it”
If someone is worried they may have blasphemed the Holy Spirit - they have not - because if they had they would not care.
Second, it is clear that no sin is unpardonable.
Let me repeat that - God will forgive all sin if the sinner repents.
The key here is ‘if the sinner repents’. If someone has committed blasphemy against the Holy Spirit they have rejected God’s witness of Himself - they have cut off their road to the knowledge of God through Christ - because it is the Spirit who testifies with our spirit that He is God. If we reject the witness of the Spirit of God, we no longer have a way of knowing or relating to God - we have effectively - by our own choice - cut ourselves off from God.
The reason blasphemy against the Holy Spirit is an ‘eternal sin’ is not because God will not forgive it - it is because the person who commits it has chosen to cut themselves off from God’s Spirit and therefore the truth about Christ, which is spiritually discerned.
I Corinthians 2:14 - “The person without the Spirit does not accept the things that come from the Spirit of God but considers them foolishness, and cannot understand them because they are discerned only through the Spirit.”