Let's see what misconceptions we can dispel (taken not just from the Question, but also from comments):
Christians bet their entire existence on a prize they know nothing about.
This is a gross misrepresentation. We don't know every detail, true, but we know we will have restored and perfected bodies, and we know we will be with God. We have many, many assurances that this existence will be wonderful in ways we can't even comprehend at this time.
In any case, thinking of it as a "prize" isn't the best attitude. Those who seek out of greed will be disappointed. The real question isn't "where will we go?", but "do we want to be with God?". For those who love Him, being eternally apart from God is unthinkable.
The one who [I am], the one who is talking to you now, will disappear when my brain die, as my mind is a product of my physical existence.
This is a very Materialist perspective, and is flatly contradicted by Scripture. Even modern science doesn't claim to entirely understand consciousness. Scripture, meanwhile, says that, while our bodies are physical, our essence, our "souls", are spirit and live on though our bodies die. Thus, according to Scripture, the belief that you will necessarily cease to exist when your body stops working is false.
I [am] happy to die and disappear.
You might. You might not. There is disagreement over what happens to unbelievers, namely, whether they suffer for eternity or (at some point) cease to exist. Personally, I believe your desire for the latter makes it more likely if it is an option at all, but do you really want to bet eternity on that?
Will I reborn in this same old planet?
Certainly not. Scripture describes a new Heaven and a new Earth. "The whole [present] creation has been groaning together in the pains of childbirth until now." (Romans 8:22) It was Cursed because of the Fall (Genesis 3). It will be recreated as it was meant to be, free from death and decay, and will be a better place. Disease, suffering and death will be no more.
We don't know exactly what this New Earth will be like, but that it will be recognizable and comfortable, and will have plants and water, is almost certain. Isaiah (11:6-9) speaks of animals that no longer hunt and kill. There may or may not be a sun (Revelation 7:16, 22:5), or oceans (Revelation 21:1). There will be at least one city, but no pollution, nor will it feel crowded.
What about climate change?
It's true that the climate can change, but God assures us that "while the earth remains, seedtime and harvest, cold and heat, summer and winter, day and night, shall not cease." (Genesis 8:22) The idea that we humans can affect the climate to such a degree as to render Earth uninhabitable is a) hubris, and b) a claim put forth by those who would deny God's existence and base their models on conjectures that are contradicted by Scripture. For that matter, some believe that Earth's climate is, in fact, improving. This is getting a bit into the weeds, however, and is an incredibly complex topic in its own right. The short version is that, no, you don't need to worry about "climate change" in the New Creation.
Must I work?
I wouldn't count on laying in bed all day and having food brought to you... although whether or not you will need to eat is disputed. However, various Scriptures suggest that food will be so plentiful that one need merely reach for it. This would suggest that you don't "need" to work. Even so, keep in mind that the toil of work will be no more. I would consider it likely that you will work, but will enjoy doing so because it will not be boring, tiring or stressful. Even in this life, many who don't need to work choose to do so.
What activities/hobbies will I pursue?
This is the most difficult question to answer, as I don't believe anyone really knows. It seems almost certain that you will worship God, as there are many examples given of His People worshiping him. I don't believe, however, that this will feel like an obligation, but rather will be something you want to do, akin to hugging a loved one. I also couldn't say whether all people will worship continuously, or whether there will be places of worship that people drift in and out of as the mood strikes them.
The world is a little bit better because of my good deeds. I'm saved.
Knowing Jesus is not a requisite.
Scripture is very clear that those who place their trust in their own works are going to be... "disappointed" when they stand in Judgment. No matter how good your deeds are (and to be sure, good deeds are commendable), your sin is worse. Without a Savior, all your good works are for naught.
The Good News is that God did send His Son to bear the penalty of your sin (and mine, and everyone's), "that whoever believes in Him should not perish but have eternal life". (John 3:16b) Only those who trust in this Promise and who seek the Lord are saved, but also those are the only requirements. Do not put your hope in earthly things or your own works, but trust in Him who alone has the power to Save.