As others have stated, it appears you have a very live and reflective room that needs taming. All of those reflections are smearing the sound from your speakers and creating a mess.
I would look at adding a large rug as well as some decorative, acoustic panels to the ceiling, first. Like you, I would try to avoid blocking my view of the sea with window coverings. On the other walls, I’d try adding more decorative panels in different sizes, wherever they could fit.
That could be a good start.