No, they did not believe that Jesus was God. Paul wrote, 1 Corinthians 8:5-6 UASV:
(5) For even if there are so-called gods whether in heaven or on earth, as indeed there are many gods and many lords,
(6) yet for us there is one God, the Father, from whom are all things and for whom we exist, and one Lord, Jesus Christ, through whom are all things and through whom we exist.
and he repeatedly wrote, e.g. Philippians 1:2 WEB:
(2) Grace to you, and peace from God, our Father, and the Lord Jesus Christ.
The Apostles believed Jesus, who said in prayer to God (his and our heavenly Father), John 17:3 UASV:
(3) This is eternal life, that they may know you, the only true God, and the one whom you sent, Jesus Christ.
But they didn't teach that! For example, this is the Gospel that Paul taught - 1 Corinthians 15:1-8 UASV:
(1) Now I make known to you, brothers, the gospel which I proclaimed to you, which you have also received, in which you also stand,
(2) by which you are also being saved, if you hold fast to the message, I proclaimed to you, unless you believed in vain.
(3) For I delivered to you as of first importance what I also received: that Christ died for our sins in accordance with the Scriptures,
(4) and that he was buried, and that he was raised on the third day according to the Scriptures,
(5) and that he appeared to Cephas, then to the twelve.
(6) Then he appeared to more than five hundred brothers at one time, most of whom remain until now, though some have fallen asleep;
(7) then he appeared to James, then to all the apostles;
(8) and last of all, as to one untimely born, he appeared to me also.
And he also wrote, Galatians 1:6-12 UASV:
(6) I am amazed that you are so quickly deserting him who called you by the grace of Christ and are turning to a different gospel;
(7) not that there is another, but there are some who trouble you and want to distort the gospel of Christ.
(8) But even if we or an angel from heaven should proclaim to you a gospel contrary to the one we preached to you, let him be accursed!
(9) As we said before, and now I say again, if anyone is proclaiming a gospel to you contrary to what you have received, let him be accursed!
(10) For am I now seeking the favor of men, or of God? Or am I striving to please men? If I were still trying to please men, I would not be a slave of Christ.
(11) For I would have you know, brothers, that the gospel that was preached by me is not according to man.
(12) For I neither received it from man, nor was I taught it, but I received it through a revelation of Jesus Christ.
No I am not a JW. You may think they're not Christian, but Google AI thinks that they are! It says:
Historians and sociologists often describe them as a non-trinitarian, restorationist Christian movement. This means they emerged from the 19th-century Adventist movement and try to restore what they believe original Christianity lost, while differing heavily from historic orthodox theology.
The main difference is that Jehovah's Witnesses don't believe in the man made Trinity doctrine, and Trinity idol worshippers don't like that so they turn nasty and try to smear them as non-Christians!
The Trinity and and "hypostatic union" nonsense were not invented 2 thousand years ago - they weren't finalised until 500 - 700 years later.
And yet the Christian 'beliefs' were changed hundreds of years later to add the Trinity doctrine!