Withdrawal taken away

I deposited €750 (no bonus) and won €4915 when I tried to withdraw they said I broke the terms and conditions as I bet more than 30% of my depot. This whole process seems unlawful and very unfair to the player and just putting the edge into your favour and far from the being in the spirit of the game. I really don’t understand why they were allowing and taking bets on outcomes I had no chance of winning. There were no bet limits when I was playing games I don’t understand Why they have you removed all the winnings even when most of the bets were placed under the 30% limit. They have offered me €1500 as a good will gesture as long as I stop any complaints is this normal

Thanks for your help

Toby