Hi Fabio, we have tried doing the same on our test server and image quality was not affected.
So, there might be a different issue with your site.
So, in order to inspect and find a proper solution, it’s best that you provide us with temporary access.
Then we can come up with a proper solution.
You may e-mail the temporary access info on support@rextheme.wpmudev.host and we will get this solved ASAP. Thanks

Hi Fabio, hopefully, you got the solution. Feel free to reach out to us if you face any further issues. Thanks