Yes, you are always able to start or stop investing at any time. Just go to your personal dashboard and hit the start/stop button. Moreover, you can always adjust the investment amount and risk profile in your personal dashboard.
If you start, your funds will be invested in crypto currencies. If you stop, your funds will be converted from crypto currencies into your base currency.
You can define the base currency in your dashboard, e.g. EURO or BTC depending on the crypto currency exchange which you’ve linked.