Hi,
To begin with... Aqua Mail is not available for PC. In Addition, Aqua Mail stores a part of your messages in the device and accesses more of them if needed and depending how you've set that. So it cannot transfer your messages to your PC.
From Gmail, for example, you can download your data to your PC. To do that go to myaccount.google.com -> Sign in with your Google Profile in there -> Personal info & privacy -> Control your content -> In the Download or transfer your content section, find the Download your data box and click on Create Archive.
Let me know what exactly are you tempting to do and we'll proceed accordingly.