Learning 3D software on a tiny budget need advice

What you need to know about me, my hardware/software before asking my question:

I currently live in Mexico and work as a volunteer for a low budget, non-profit aerospace R&D organization that hopefully might become big someday. My goal in the long run is to be able to use a mixture of blender and CAD to design/invent parts for aerospace craft designs. However, I do not have the money to go to a college, and it took years just to get the money needed to custom build a CAD workstation that I'm currently using.

For the moment, my windows 10 pro 64bit based CAD workstation is running Blender 3.2.2 and I have a 3090 for a video card. Long story how I was able to get a 3090. Had to sell some stuff to get it haha. Anyway, the leader of the aerospace organization who is currently tutoring me on learning Blender, explained some differences to me between Blender and CAD, and said that I need to eventually learn both to accomplish my long term goals.

I've been learning Blender for a few months now and so far I finished a 16 lesson donut tutorial, and a "how to create a realistic looking earth" tutorial by Blender Guru on Youtube just to 'get started' on Blender and now I'm in the middle of a super complex 46 lesson tutorial on how to 3D model and animate the 1960's USS Enterprise based on actual blueprints on the studio model lol.

And now finally, my question:

1. Since there are so many ways to learn things on the internet for free and I have a CAD workstation, due to my specific goals, what is the best free CAD software that you guys recommend?

2. Due to the many ways to learn skills online for free, are there any specific youtube tutorial series or free online classes that you recommend for whatever free CAD software that you recommend?

3. Is there any advice that any of you experienced Blender and/or CAD workers have for a rookie like me?

I'll figure this out on my own, but I thought it would be a good idea to leave my three questions here while I search for the answers on my own. And to be clear, one day when I have the money I plan on getting my hands on the best CAD software/hardware I can get but until then I have to work with what I got. So please don't recommend CAD software that isn't free cuz I don't have the money for it right now.