Room Treatment suggestions and advice


Hi folks,

I'm coming here asking for advice. First of all I understand I need to do some experimenting myself with positioning, toe in etc, which I will due in due time, but regardless of that I'd like to ask for some advice on some room treatment options.
Here's a link to some photos/drawing of my room (explained later)https://imgur.com/a/C6D3IhC

I have recently moved to a new house. I am renting so my options are potentially limited (even though I could drill holes in the walls to hang stuff as long as I cover the holes after the tenancy ends so don't want to discard this option). I am also in the Czech Republic, nearby Prague, so that may limit slighly where can I buy products from, even though I have already found some online shops with audio treatment stuff (mostly MegaAcoustic stuff coming from Poland).

I am planning on setting up my stereo system in a room that is rectangle shaped, quite long (2.6 meters by 8.5 meters roughly). I have attached some pictures that I will be referencing throughout the post. On one end of the room I have a desk where I'll be working (I will work from home even after the pandemic is over). Then I have a kallax separating the room into two spaces, and I was thinking of having my stereo setup on the other end of the room.

I have placed the speakers but at the moment because of the room geometry and the empty walls, the acoustics are terrible. It's very boomy and echoes a lot. So I'd like to ask you people what decent audio treatment options I could try to try and improve things. I am not necessarily looking for a perfect setup, just something that doesn't suck (as it does at the moment) or gives me the best bang for the buck.

I have attached some photos where you can see the room and some floorplan/3d renders. I have added some annotations on them with numbers so I can easily reference them in here. Units in the photo are in centimeters. (also bear with me, this setup is temporary, I will be getting rack for the DAC/Amp and that cardboard on the bottom of the speakers will be gone).

The first 2 things I would definitely like to do are:
- Have a curtain pole and a curtain to cover the back wall (number 3).
- Have a nice thick carpet on the floor (number 4).

Now, when it comes to more things, I'd like to know what are your thoughts on:
- Current positioning of the speakers (distance from the walls) and current listening position? Unfortunately those doors will be difficult to deal with unless I can find some portable panels I can easily put and remove when I do a listening session.
- Adding some bass traps in the corners by the back walls (between 1 and 3, between 1 and 2)
- Should I also add some acoustic panels on the walls 1 and 2? I think there are going to be some early reflections there (I still need to do the mirror technique to find out exactly where those are).
- Finally, what to do with walls 5 and 6? I have some IKEA billy bookcases to put into the room but they are the ones with glassdoor so that's not ideal as I think they'll be quite reflective. Do you think I should be looking into normal bookshelves, or not have those at all and have some more acoustic panels hanging in there? Unfortunately the gym bars I won't be allowed to remove.

Any other comments or suggestions would be greatly appreciated.
Here's a link to the photos:
https://imgur.com/a/C6D3IhC
And here are the kind of panels I was thinking of: https://www.muziker.cz/mega-acoustic-fiberstandard120-black

Thanks for your time!
melindro
Building bass traps are easy and less expensive than buying.  You can save a lot of money that way. 
The ones you linked should work fine, especially if they are local to you instead of shipping across the world. I would put a heavy curtain over the window so you can open during the day if you want for some light. Experiment with the panel placement before you attach them if you planning on attaching them and some kind of rug in front of the speakers.