If you are faced with having positive earnings (€) and negative returns (%), or the opposite, do not worry. Even if it sounds wrong, it is quite correct! Returns are calculated separately from contributions and withdrawals. If your return is positive, it is because your portfolio has increased in value since your first investment. Conversely, if your return is negative, it is because the value of your portfolio has decreased since your first investment.
If your monetary gains are negative, it is because you deposited the majority of your investment just before the value of your portfolio fell. Conversely, if your earnings are positive, it is because you deposited the majority of your investment just before the value of your portfolio increased.
On Monday you invest 1000€. On Tuesday, the markets have risen by 10%, so you have gained 100€ and your portfolio is now worth 1100€. You then add 2000€ in the evening and your portfolio is now worth 3100€. On Wednesday, the markets are down by 5%. Your portfolio is now worth 2945€. This translates into a net loss of 55€ on the 3000€ invested in total. However, the performance in % will be 4.5%, i.e. positive: (1+10%)*(1-5%)-1 = 4,5%.