1. bitcoin is already a global currency. you can right now send bitcoin to anywhere in the world in less than 10 seconds and have it included in a block in less than 10 minutes on average. this can be sending money to family in your home country, or it can be buying some digital or physical goods.

2. price is still volatile, and bitcoin is still in beta which you may even refer to as an "experiment". the potential is there and many (including me) believe bitcoin will be a lot bigger and adopted more in the future. but this does not eliminate the risks. you always have to invest what you can afford to lose.

3. if you want to buy "Lambos and Nintendo Switch" you have to find someone who is accepting bitcoin as payment and sometimes that is hard, not impossible but hard. so your only option is to sell for fiat and use fiat for that unless you live in Japan LOL.