i want to download CURL and used https://macappstore.org/

FYI ... CURL is already part of macOS. There shouldn't be a need to download it.

You don't have to worry about this as you are lucky that there is nothing nefarious here with those instructions.

The instructions on that page had you install HomeBrew which is a third party command line utility to provide an easy way to install open source utilities on macOS or Linux which may not be included in the OS (or newer versions of those items than those available from the OS).

Homebrew is generally "Ok", but there are some caveats and should not be used lightly or without proper understanding. Sometimes Homebrew may unintentionally break parts of macOS. It can also be tricky when HomeBrew is used to install command line utilities already built into the OS...which version of the utility is getting used (the native built-in macOS version or the Homebrew version)? If macOS does not properly use the full path to the utility, then the Homebrew version of the utility may be used, but this may cause problems because it will be a newer version with possibly different behavior.

For this reason I try to avoid using utilities like HomeBrew (or MacPorts, etc.) except on a separate disposable installation of macOS where I don't care if things break. I try to avoid using this on my main system.

FYI, people should be very cautious blindly entering commands within the Terminal app without understanding what those commands will do. A person should also consider how to reverse the actions of any commands used before attempting to use any commands including backing up any files which will be modified. The command line has no safety nets and is very unforgiving. Even a person with decades of command line experience can make a simple mistake (as simple as mis-typing one character) where it may break the OS or destroy all their data. Beware of any instructions which don't also explain how to revert back (this applies to any app you install).

Most likely Homebrew also installed the XCode Command Line Tools package from Apple. I have no idea on the proper method for uninstalling those tools...really no need to remove the XCode Command Line Tools.

Before trying to reverse the process, make sure you have a good backup of your system in case something goes wrong with these instructions.

I did a bit of quick research, but it will be a lot more involved to reverse everything especially since you are not familiar with the command line. You are best just to leave everything as it is now.

FYI, if you look at the instructions you originally followed, you will see that you actually used the built-in macOS "curl" utility to download Homebrew in Step#2 of the article you linked. You should have a good reason for installing anything through Homebrew (even Homebrew itself) unless you are doing so on a test system.

Before using the Terminal app again, you should definitely read some articles on how to use the command line. Here is one introduction to the Terminal app & command line:

https://scriptingosx.com/2017/07/first-steps-in-terminal/

When learning to use the command line, it is best to use an older computer (or an OS in a VM, although this latter option still poses risk to your host system & its data) which can be easily erased in case something goes wrong. People will make mistakes while learning to use the command line no matter how careful a person is. That is how unforgiving the command line is. Even when you know a particular command is safe, make sure to have a good backup of your system first just to be safe, since just a simple typographical error can make a big difference between success and possible data loss.

You are lucky that the instructions you followed were not nefarious.

Good luck.

I would be extremely warily of the site. If you find an app that you might want go a Google search for it and go to the developers site to download.

I did a search for an app that I use a lot and got this:

I don't know what brew cask is but it's not needed to install AppCleaner. I prefer looking for apps on MacUpdate.com. I don't download from the site but they do have a link to the developer's site from where I can download.