To answer your question, Bitcoin is only the "deposit method" when making a deposit.
As soon as we receive the deposit in your account, the amount is credited and valued in EUR or USD (based on the average Bitcoin rate at the time you sent your Bitcoins).
We then make this investment work by converting it into crypto-currencies or FIAT currencies (e.g. EUR or USD) as arbitrage opportunities arise. On the last day of the month, your earnings are calculated in EUR and added to your initial balance (also in EUR or USD).
If you had kept your Bitcoins as is (instead of depositing them with us), you would have indeed lost more than 50% over the day.
Our platform allows you, while investing in crypto-currencies (such as Bitcoin), not to bear the risk of their fluctuations (generally much higher than on other assets), but on the other hand to take advantage of them. Indeed, arbitrage in cryptos consists in making gains on the spreads and thus on the variations of the latter. The more they fluctuate, whether upwards or downwards, the greater the potential gains.
So, in summary, your investment made with us using Bitcoins would not have lost anything, quite the contrary (+8.24% gain in March 2020).