OP investment is different from gambling it is only in gambling you gamble what you can afford to lose so that you will not be disappointed in investment you don't have to worry because your funds never lost. And all what you have to do is to plan your investment very well. Either long term or short term.
Let's be specific here, some investments aren't safe and a lot of them are lost when done wrongly, in crypto space, a lot of shit coins drain peoples fund constantly, but investment in bitcoin is very safe because of its feature as a store of value.
2. Investing what you can afford to lose: this means that you're using your money to buy something that you can lose at any time. If that's the case, it means it will be unwise for someone who's earning 200k per month to keep investing 40k for multiple years.
Wrong impression, when the term investing what you can afford to lose is initiated in bitcoin investment, it doesn't in any way man you're investing for the purpose of losing it or you can lose your investment entirely, else its no different from shit coins.
It simply means invest an amount that your living and activities doesn't depend on and you'll not be needing anytime soon, so you can invest it for a longer time for it to be profitable. Bitcoin price fluctuates, the price is unstable, but your investment appreciates greatly with time if you invest long enough, let's say a minimum of 4-10 years without tampering with it.