As soon as you installed the program, especially when we are talking about programs downloaded from the internet, you can safely delete the downloaded installation file from the Downloads folder. As a method, to help you identify the older files, you can sort the files in the Downloads folder by date, in ascending order (that is, from the oldest to the newest), by opening Files Manager, going to the Downloads folder and clicking on the Date Modified field, on the right side panel, once or twice. When you'll see a small arrow, on the right side of Date Modified, pointing up, then you will have the files sorted from the oldest to the newest and you can start deleting without worrying.
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