I’m 21, totally new to investing, joining the Canadian Armed Forces soon need beginner advice

Hey everyone,
I’m a 20 (almost 21) year old guy from Ontario who’s about to join the Canadian Armed Forces. I know almost nothing about money stuff beyond saving in a regular bank account. Stocks, portfolios, ETFs, TFSA, RRSP – these words might as well be another language to me. I’m starting from zero and I really don’t want to make any dumb mistakes.
Here’s my situation:
• I currently have about $35k saved.
• But I owe $32,500 to OSAP (student loans) that I need to pay back soon.
• After paying that, I’ll basically have around $2k left.
I’ve heard people say you should have 6 months of expenses saved as an emergency fund before you start investing, which makes sense to me and I plan to do that first. But I’m still thinking ahead and wondering what I should do with any extra money once I have that safety net.
I’m considering opening a Wealthsimple account because it seems simple and beginner-friendly. My questions are:

1. Should a total beginner like me even open a TFSA right now? Or is there something better/safer for someone in my position?
2. What would you actually do with $2,000 (or small amounts going forward) if you were me?
3. Can someone please explain this whole thing like I’m a 5-year-old? How does investing actually work without me losing all my money?
   I’m not looking for “just buy X stock” answers. I want to understand the basics first. Any advice, resources, or simple explanations would mean a lot. Especially from people who started with very little knowledge.

Thank you so much! Appreciate any help