I've undergone quite a bit of research in to "breaking" your metabolism. In short its absolutely 100% possible. In fact, I've done it. If you get cancer and have a total thyroidectomy. You can outright kill your metabolism to the point you really will die in about in 2 months time without thyroid hormone. Trust me. I was at 1.5 months before I started my hormone replacement(thanks covid!). It absolutely sucked. It's not just your metabolism, but every function in your body steadily slows down.
It's a 2 fold effect. It's a natural process. You will slowly start eating less but at the same time, your body does indeed go into starvation mode. You won't loose weight. Might even gain weight. This is being in hypothyroidism.
The same can be said for hyperthyroidism. Your metabolism is increased and you will eat more naturally without noticing, but at the same time burn just ever so slightly more. I'm struggling with this now. My increased metabolism causes me to just crave more food. It takes more to be satisfied. I have cravings more. Due to my hormone replacement and being slightly in a state of hyperthyroidism. But the body doesn't burn that much more though. With an increased metabolism, you can gain weight faster quite fast.
It really comes down to knowing your body. Adequately and appropriately adjusting your activity levels and eating in a deficit. Having a high or low metabolism can both cause you to gain weight. We have a natural basal metabolic rate. While thyroid hormones play a function in this. Our body composition makes a difference as well. The act of being active burns calories, but also builds your muscles. Naturally Having more and bigger muscles will naturally burn calories, just a little more though. This is a 2 fold effect. But then again, as I can personally attest to, an increased metabolism increases your appetite. You can't just build muscle for a month then hope to burn calories. You have to be active, and the more you're active, the less you're eating. This becomes the theory that "hype nutritionists" work pander to desperate people trying to lose weight. Yet it's not completely understood.
Go see a doctor, figure out what all your hormone, blood test levels, vitamin/mineral deficiencies are. Your need to research your own body. What it will turn in to is a calories in/calories out. Increased activity will help burn calories, but not as much as you think. 1 hour of exercise could very well only burn an extra 100-200 calories a day. But you may end up overeating that 200 calories burned just as easily.