It's a marathon, not a sprint.
That quote has been echoed repeatedly, especially in the health and fitness world. Unfortunately, it's meaning is often thrust to the wayside, replaced with hopes of quick fixes and simple solutions. The marathon to becoming a healthier version of yourself is certainly not quick, but small steps will get you much farther than you may realize.
Losing weight seems very difficult in practice, but it's fairly simple on paper. Enter your information into a TDEE (total daily energy expenditure) calculator (https://tdeecalculator.net/) to find out how many calories a day you need to eat to maintain your weight. Once you have that number, simply subtract 300-500 calories. Stick to that number and over time, you'll notice yourself dropping body fat. You can safely assume to drop 1-2 pounds per week. While not a "lose it all in 6-weeks" scheme, by the end of a year you could be down 50-100lbs. Remember that it certainly didn't take a mere 6 weeks to add the weight.
If you're on the other end of the spectrum and you're trying to gain weight, simply add 200-300 calories to the maintenance number you calculated earlier. Combined with a consistent resistance training schedule and enough protein, you'll find yourself packing on 1-2 pounds of extra muscle per month. While not a "get huge quick" plan, you could add 10-20lbs of muscle by the end of a year.
If your goal is to get stronger, you'll first need to find your base level of strength. Just like the calorie equation we used, once you find your "maintenance" strength (try a max set of pushups), you simply need to add either more reps, sets, or resistance to your training program. Executed properly will afford your body the stimulus it needs to grow stronger. Over a few years, I used these strategies to bring my deadlift above 500 pounds and increase my max pullups to 25.
You might be feeling that the strategies I mentioned above sound too easy. That's because they are easy. Easy on paper, difficult in practice. If you read back, all units of time are noted in years. It's written that way to demonstrate that small changes such as adding or subtracting a few calories each day (a small step) can lead to big fitness results. However, it's always important to remember that it's a marathon, not a sprint.