I believe that 1 Corinthians sums up what the Holy Spirit does for the believer.

It says; “The Spirit searches all things, even the deep things of God. For who knows a person’s thoughts except their own spirit within them? In the same way no one knows the thoughts of God except the Spirit of God. What we have received is not the spirit of the world, but the Spirit who is from God, so that we may understand what God has freely given us.”

So just like everyone has a spirit, and that spirit in you knows your inner thoughts.

So is it with the third person of the Trinity. The Holy Spirit knows the mind of God because, he is God himself.

When the Bible says baptizing them in the name of the Father, and of the Son, and of the Holy Ghost.

What else could it mean when it places all 3 as God, but yet it is but one God.

The Father the Son, and the Holy Ghost make up the Godhead.