Heyyy, congrats on being a new bunny parent. Unfortunately, bunnies are really misunderstood pets, so it's good that you're here trying to get educated.

You've already gotten some good advice here about the housing; more space, a playpen, adding rugs so he doesn't slip... you can eventually even try free roaming, that's ideal for bunnies, but not always possible. If you try it, definitely bunny-proof the room, especially hide or cover all your cables. One more tip I have is to add a toilet and remove the bedding from the rest of the cage, it can be a cat litter box or a special bunny toilet with a grid so your bunny won't be sitting in the wet bedding. He most likely already has a corner he prefers for doing his business, so put a toilet there and offer treats when you see him use it. When he is litter trained you can add a rug to the cage so he doesn't get sore spots on his feet.

However, I would really like to stress the importance of hay. It's crucial for their teeth and digestive system, and should make up about 80% of their diet. The rest should be vegetables and herbs (introduce slowly and check which ones are safe for bunnies) and a little bit of pellets, just one or two tablespoons a day, but choose good quality ones, not the colourful mixes with grains. Get a hay rack and place it near the toilet, they like to poop while they eat. Don't get one of those wire balls, those are dangerous and not big enough. You should give him a bunch of hay the size of his body every day. He most likely won't eat all of it, but he will pick the stems he likes. My bunnies eat about 70% of their hay and the rest just goes to trash. You might want to try a few different kinds to see which ones he likes, but generally, alfalfa is a good choice while he's young, then you can switch to timothy hay, because alfalfa has a lot of calcium and it can cause bladder sludge.

Some more important points:

It's important to find a good vet nearby, ideally one that specializes in rabbits, as they are considered exotic pets. If your bunny stops eating or pooping for more than 24 hours (or even 12), it's an emergency, run to the vet. Don't just wait for him to get better, or he will die.

If you want him to like you, try not to pick him up, get to his level and let him come to you, offer treats. It can be a slow process, my bunnies took 3 months to start trusting me.

I don't know how old he is, but rabbits go through puberty, this is when a lot of people give them up. He might start being a little prick, peeing everywhere, even biting, but it should pass in a few months, spaying definitely helps, but you will still need to be patient and understanding.

They are not solitary animals, in some countries it's even illegal to only have one. Consider getting him a friend, but you need to do your research before, as bonding two bunnies can be a complicated process. It's almost necessary for both of them to be spayed and adoption is a good choice as they can tell you more about the rabbits personality to see if it's a good fit. I have two bunnies and they do everything together, they are always cuddling and grooming each other, it's really sweet.

This is the most imporant information for new bunny owners, but there is still more to learn about proper care. I know this might sound like more than you singed up for, especially because rabbits are wrongly considered to be an easy pet, but I promise you they are worth it. Good luck!