Expenses when you have no income yet

You can certainly claim expenses, even without any turnover. Starting up a business costs money, while you may still be searching for customers.

Even making a (limited) loss in your first year is perfectly fine, it can happen. This may be a result of having expenses for a few months before you start generating turnover.

So no problem! ;)

Yes, I also made a loss in my first Dexxter year (2021). Barely any income, but some costs, so I asked my advisor for advice, but that was fine.

Making a loss in your first year (without turnover or with little turnover) is perfectly fine.