If you have the error stating that your balance is insufficient, it means that the amount you are entering with is less than the minimum trading amount.
Please make sure that:
1) Your balance in the trade is more than 20$. This is the minimum trading amount allowed on WunderTrading.
2) Your FREE balance is greater than 20$. The free balance is the amount of funds not used in any other position on your exchange.
3) You have the asset in the base currency that you are trading. For example: if you are trading ETH/BTC and going Long you will need to have BTC in your exchange account and not USD.
If none of the above helps, feel free to contact our support by clicking the Support button located in the navigation panel on the left side of your cabinet.