All of the UI needs work. The font and icons are very small which makes it hard to read and understand. The information has an unintuitive layout. Why is the price of what I’m buying not on or around the buy button?
Try making something like this:
Roblox stocks actually doing well nowadays.
The stock price is shown, the price increase over the past day (but for the game, maybe a minute would be better), and it shows a chart of the price over time. You can create fake stories that would appear as well, making the game feel more alive. These stories would show up in a feed and seemingly effect the stockholder’s choices. Something bad would make people sell and lowering the price, and something good would make people buy and hold more often, raising the price.
For the game, you could place the buy button right beside this, although it’s more complicated in real life. This UI also gives you an opportunity to give your made-up companies a branding style, like Roblox has.
There should be a clear progression path for the user. Allow the user to see more and more expensive stocks that they will work towards, allowing them to gain (or lose) more money.
You need to understand the target audience this game would have. It’s much too complicated for a kid to understand, so design your game to be addicting to teenagers and young adults. That means… no pets. Sorry! They didn’t make sense anyways. To work towards making a popular game, your game’s overall style and target audience should match.
Still, the attention span of a teenager is not that good, but it’s better than a gen alpha’s. The tutorial doesn’t do a great job at explaining how the game works right now. Assume the user knows nothing about stocks. Walk the user through the game as they play for the first time, instead of explaining everything in one shot and leaving. Focus the action they need to complete so it’s easy to understand the gameplay loop. You can do this with an arrow, darkening everything unimportant on screen, circling it, putting a big mouse icon over it, and so on.
I also noticed the use of AI in the thumbnails, for some icons in-game, and for the music. I hope these are temporary! They can be easily spotted by people and may push them away simply because they know how it was made. Regarding the music, you hear how bad it sounds before you hear it was made by AI… so I recommend changing that to a song the Roblox audio library provides. Trust me, there are some good songs in there, it just takes a lot of searching and listening!
For thumbnails, actually show your game and how it can be fun. Your thumbnails and game icon will set the user’s expectations, and the game itself should satisfy that. It’s almost as if these have to match to be the most effective!
That’s all, I’m too tired to write more. Have fun developing! You’ve got a good start. 
also the bosses are pretty big 
so trade to accumulate your wealth spend that wealth to show off and open lootboxes, hangout, defeat bosses, explore and have fun!
I’ll make a stock trading game and a Pet sim that would make the best sense, and yeah I will search the library for the songs etc I was never good with art and sounds so I just threw in these 
I’ll give my best to make a good game