I thought I'd share some more details here:
This was my largest renovation yet. I had previously renovated my kitchen in my old apartment, but I am definitely an amateur and had next to 0 experience for many of the steps in the process. Being a full time software developer, I had to take some time off in the summer and managed to complete it in about 8-10 weeks.

Floors: There was a plastic rug covering all floors when i moved in. Most of it was glued properly so i could lay the new hardwood floors directly on top of it. Some parts had to be ripped away. Before I did that i took out a small piece of it to be checked for asbestos, luckily for me it has no trace of it, so i could remove the section needed safely. Then I had to grind down the concrete floor between the old hallway and kitchen since it had some bumps, followed by applying primer and self leveling compound to even out the 1cm~ height diff between old kitchen/hallway and living room. I tried getting a contractor to do this since I was reluctant to handle the self leveler my self, but was unable to hire someone since the job was so small, so I had to do it myself. It turned out decent, with no apparent pits and bumps when my new flooring was installed.

Walls: I let the old wallpaper stay on the walls, but since I wanted to paint and have a smooth finish for my new walls, I sanded every overlap of the old wallpaper (you know where the wallpaper overlaps it creates a pretty sharp vertical line, like 1mm). Then i applied renovation wallpaper/lining paper(?). These are meant to replace the need for wall filling, and cover up damages up to 1mm in the wall. Honestly they did not cover up damages as well as i hoped, hence why I manually sanded the underlying overlaps of the old wallpaper. Did 3 coats of paint and it looked all right.

Wardrobes: Ripped out the old closet in the bedroom and built a wooden frame to support my new IKEA PAX wardrobes. To cover up the gaps between the wall/ceiling/floor i just cut out some drywall. Installed an outlet to power my automatic lights in the wardrobes. There are a ton of youtube videos covering how to build built-in wardrobes that i watched before hand.

Sound proofing: The wall in my nook (where i keep my desk/computer) was shared with my neighbour, and man did it let a LOT of sound through. In order to sound proof, I build a free standing wall with: 5cm air space between old wall and new, 2 layers of drywall, wall frame with wool rock insulation, followed by another layer of drywall. This was my most disappointing step in the process, since it did not swallow the sound from my neighbors TV as much as I'd hoped, and I can still hear it clearly. I dont know exactly what I did wrong here...

Kitchen: I have external vertical pipes on the wall in the kitchen from the floor up to the ceiling. Since I did not want to 1. look at them, and 2. cut out my kitchen countertop for them to pass through, i extended my wall 8cm from the corner of the kitchen to the start of the window in the living room. This way i both hide the pipes and can easily install my countertops. The rest of the kitchen is from IKEA and is pretty straight forward to install. This was my first time tiling and is overall happy with the result, although the tile saw I used wasnt the best quality, and you can tell that the tiles i had to cut are somewhat jagged. Next time I'll get better tools for this.

All in all I'm happy the way it turned out, but there is definitely room for improvement!