You are in the right decision. Now is the golden time to buy Bitcoin. After holding Bitcoin in 2024, it has fallen significantly from the ATH value. But if you invest and keep it for a long time, it will surely increase. No one can say exactly how many years it will take. You want to sell your mobile and invest in Bitcoin, I welcome your initiative. Because you want to sell one asset to make another asset. If you are lucky, you will definitely get an opportunity to buy an expensive iPhone instead of a mobile phone. Don't panic if you see a lot less money than you made.
I don't think you have been following the market or have any awareness about it because the market hasn't yet fallen significantly from the ATH because the new ATH was a little above $73k and Bitcoin is trading above $66k right now, so that is just a difference of $6k which I don't think is a significant difference when it comes to Bitcoin and its volatility.
There is nothing wrong if someone buys Bitcoin at this point because we are still anticipating a bull run in the next couple of years so if that happens, those who are buying Bitcoin at current price will still get to have a lot of profit from their investments regardless of the fact that they could get more if they had bought earlier but some people were probably not around when it was cheaper.