Converting an old tool shed/chicken coop into a guest bedroom. Looking for advice on soundproofing and insulation.

Hi everyone. I have a small rectangular room that I want to convert into a guest bedroom. The main goal is to have it well insulated from outside noise (and ideally from rain noise on the roof, if possible). Here are the current details: 📏 Measurements and structure: Floor: 8'2" x 11'7" (currently has a rough concrete screed). Walls: 4" thick bricks (laid on their narrow edge). They are quite thin. Roof: Sloped corrugated metal sheet. Wall height ranges from 7'9" on one long side down to 6'7" on the other. Current openings: A small window (27" x 16") and a door (27" x 5'10"). 📍 Context and limitations: Party walls: Two of the walls (forming a corner) are shared with my neighbors. Current use: It used to be a tool shed/chicken coop, so the floor is rough concrete and there's no insulation anywhere. Location: Greater Buenos Aires suburbs, Argentina. Budget: Medium budget, and I'm open to doing the work in stages if that makes sense. ❓ My main questions: Walls: How should I approach soundproofing the 4" walls, especially the two shared with the neighbors? Would it be worth taking advantage of the thin walls and applying a cement-based waterproofing coating (like "Ceresita," a local hydrophobic additive we mix with cement) on the exterior/neighbor-facing side? Or would it be better to build an inner frame with glass wool/rock wool insulation and drywall? Roof: Since it's a metal sheet, noise and temperature will be issues. What do you recommend for a false ceiling or attic space to insulate it properly? Floor: What are my options to level and insulate the floor starting from the rough concrete screed? Openings: Should I replace the window and door with double-glazed aluminum ones, or are there budget tricks to improve the current ones? Any advice on the order of work or recommended materials would be greatly appreciated. Thanks!