Thanks so much!
Don't worry, after a month all I had was very basic horizontal and vertical movement. This is me more than two years into my journey.
For level design, I have a few resources for you.
I made a level design video a few days ago but not many people saw it. That's like a good overview of the philosophy and process I use personally.
GMTK's level design videos are all fantastic, highly recommend you watch those.
Let's Talk Game Design is another great channel. That one has a lot of 2D Platformer-specific stuff.
As for the movement mechanics, LOTS of trial and error. I probably spent over 300 hours on the movement alone (between implementation and tweaking variables).
Here's how I do jumping: video
A great overview of 2D movement
GMTK on the theory behind good movement
Good luck!