I have searched high and low for a proper community to post this question in. I’m trying to find something to cover this window that’s easy to remove (apartment)

My apartment has tall ceilings and im a single male so of course there’s nothing on the walls lol. This place has an an echo as bad as all get out. I’m slowly trying to fix that.

So I’m trying to find something that I can stick to this window that helps a little bit with acoustics and at the same time I want to eliminate the window as a light source completely. The problem is it needs to be easy to remove because I’m renting. I’m fine with it requiring a little bit of work to remove because I intend for it to be permanent throughout my time living here, just want to avoid damage. I figured I would ask the community because there’s usually someone who has been through something similar that has good advice. Thank you for taking the time!