Help me get out of my obesity please🙏

I'm a 19-year-old male, 5'10" and 105 kg.

For the last three years, I was completely focused on preparing for a competitive exam. Now that I've finally cleared it, my first and biggest priority is improving my physical health and getting into good shape.

I know I'm currently obese, and I understand that getting lean won't happen overnight. Realistically, my first goal is to look lean and healthy within the next year. Beyond that, building a genuinely impressive, "flex-worthy" physique is something I know could easily take 4–5 years of consistent training, proper nutrition, and discipline. I'm not looking for shortcuts—I know it takes time, and I'm ready for the journey.

Spending long hours sitting and studying has taken a toll on me. My knees hurt, my lower back feels stiff, my joints crack when I move, and my overall mobility has become poor. Even my posture, hand strength, and general fitness have suffered because of years of being sedentary.

But now it's time to change that.

I'm determined to transform this body, not just for aesthetics but for my health, confidence, and quality of life.

I'll be joining a gym in July after returning home around June 25. Since I have absolutely zero gym experience, I'm honestly a bit nervous about my first day.

I've been trying to learn as much as possible from YouTube, Gemini, and other sources, but I'd really appreciate guidance from people who have already gone through a similar transformation.

How should I start? What should my first few weeks in the gym look like? My goal is to become lean within a year and then gradually build muscle over the following years. Any beginner-friendly workout routine, nutrition advice, or Day 1 tips would be greatly appreciated.