If you have traded cryptocurrencies, you are required to show your transactions in your tax return regardless of whether you made a profit or made a loss. The text below is translated from the Swedish Tax Agency's website:
If you have sold, exchanged or paid with a cryptocurrency, you need to report this to the Swedish Tax Agency in connection with your declaration. If you have made a profit, you must pay tax on your profit, and if you have made a loss, you may deduct part of it. Cryptocurrency is also called virtual currency or digital currency. - The Swedish Tax Agency.
You can read more about what the Swedish Tax Agency writes about cryptocurrencies through this link: https://skatteverket.se/privat/skatter/vardepapper/andratillgangar/kryptovalutor.4.15532c7b1442f256bae11b60.html
Safello cannot give advice or instructions on how to declare and therefore we advise you to contact the Swedish Tax Agency directly to get answers to your questions regarding the taxation of cryptocurrencies.