Jehovah or the Holy Spirit?

Isaiah 6:8-10 NWT

And I began to hear the voice of Jehovah saying: “Whom shall I send, and who will go for us?” And I said: “Here I am! Send me.” Then he said: “Go, and say to this people, ‘You will hear again and again, but you will not understand; You will see again and again, but you will not get any knowledge.’ Make the heart of this people unreceptive, Make their ears unresponsive, And paste their eyes together, So that they may not see with their eyes And hear with their ears, So that their heart may not understand And they may not turn back and be healed.”

"Who shall I send, and who will go for us?" 
Who is speaking and who is the "us" being referred to here?
Acts 28:25-27 NWT

“And as they were disagreeing with one another, they began to depart, Paul made one comment: ‘The holy spirit aptly spoke through Isaiah the prophet to your forefathers, saying: ‘Go to this people and say: “You will indeed hear but by no means understand, and you will indeed look but by no means see. For the heart of this people has grown unreceptive, and with their ears they have heard without response, and they have shut their eyes, so that they might never see with their eyes and hear with their ears and understand with their heart and turn back and I heal them.”‘

The Holy Spirit speaks? And speaks as Jehovah?
Jeremiah 31:33-34 NWT

“For this is the covenant that I will make with the house of Israel after those days,” declares Jehovah. “I will put my law within them, and in their heart I will write it. And I will become their God, and they will become my people.” “And they will no longer teach each one his neighbor and each one his brother, saying, ‘Know Jehovah!’ for they will all know me, from the least to the greatest of them,” declares Jehovah. “For I will forgive their error, and I will no longer remember their sin.”

Who is speaking here? Jehovah, right?
Hebrews 10:15-17 NWT

Moreover, the holy spirit also bears witness to us, for after it has said: “‘This is the covenant that I will make with them after those days,’ says Jehovah. ‘I will put my laws in their hearts, and in their minds I will write them.’” Then it says: “And I will no longer call their sins and their lawless deeds to mind.”

Who is speaking here?
Psalm 95:7-11 NWT

“For he is our God, and we are the people of his pasture and the sheep of his hand. Today if you listen to his voice: ‘Do not harden your heart as at Meribah, as in the day of Massah in the wilderness, where your forefathers put me to the test; They challenged me, though they had seen my works. Forty years I was disgusted with this generation, and I said: “They are a people who always go astray in their hearts, and they have not come to know my ways.” So I swore in my anger: “They will not enter into my rest.“‘”

Who is saying all of this?
Hebrews 3:7-11 NWT

“Therefore, just as the holy spirit says: ‘Today if you listen to his voice, do not harden your hearts as on the occasion of provocation, in the wilderness, where your fathers put me to the test, despite seeing my works for 40 years. So I was disgusted with this generation and said: ‘They always go astray in their hearts, and they have not come to know my ways.’ So I swore in my anger: ‘They will not enter into my rest.’

Why is the Holy Spirit speaking the words of Jehovah?
2 Corinthians 3:17-18 NWT

Now Jehovah is the Spirit, and where the spirit of Jehovah is, there is freedom. And all of us, while we with unveiled faces reflect like mirrors the glory of Jehovah, are transformed into the same image from one degree of glory to another, exactly as it is done by Jehovah the Spirit.

So there's "Jehovah" and "Jehovah the Spirit"?
Isn't that two Jehovahs?
2 Samuel 23:2-3 NWT

The spirit of Jehovah spoke through me, And his word was on my tongue. The God of Israel spoke; The Rock of Israel said to me: ‘A ruler over men should be righteous, Ruling in the fear of God.'”

The Holy Spirit was telling David what to say and spoke through him?
But the "God of Israel" spoke?
Psalm 139:7 NWT

“Where can I go from your spirit, And where can I run away from your face?”

The Holy Spirit is omnipresent?
Isaiah 40:13-14 NWT

Who has taken the measurements of the spirit of Jehovah, And who can instruct him as his adviser? With whom did he consult to gain understanding, And who taught him the path of justice And taught him knowledge And showed him the way of understanding?

The Spirit is infinite? 
The Spirit knows everything?