Design for a studio, all advices are welcome

So I'm french and I'm planing to build a recording studio in 2007, 6 months of work (January to July) for studio and home. I've already the building, it's around 120 m² and 2.48 m height without floor and ceiling. I post what it looks like now and what I want to do, plz could u help me coz I wonder if it's a good design or not ... There is also a beam of 30cm height and 20cm width and 2 pillars of 20/20 cm I can't remove ...

And then my plans